These verses (Quran 2:216-218) were revealed concerning an incident that happened in Nakhlah, in which Abd Allah b. Jahsh and his men killed a man by the name of Amr Ibn al-Hadrami, which belonged to the Quraysh (Tafsir al-Jalalayn, Tanwir al-Miqbas min Tafsir Ibn ‘Abbas and Asbab Al-Nuzul by Al-Wahidi and Tafsir Ibn Kathir)
A brief overview on the Nakhlah incident. As we have documented before, a unit of Abdullah ibn Jahsh was sent to the area called Batn Nakhlah. Their mission, as is recorded in Ibn Ishaq and other sources was to monitor the movement of the Quraysh enemy, and report back to the Prophet (p) accordingly. This was their only task (See evidence: here and here). But some of the Companions of the Prophet (p) didn’t listen to the commands given, they attacked the Quraysh’s men. When they came back to Madinah and told the Prophet (p) what they did, he was not happy with what they did. Hence this verse revealed concerning them.
2:216 Fighting has been enjoined upon you while it is hateful to you. But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah Knows, while you know not.
2:217 They ask you about the sacred month – about fighting therein. Say, “Fighting therein is great [sin], but averting [people] from the way of Allah and disbelief in Him and [preventing access to] al-Masjid al-Haram and the expulsion of its people therefrom are greater [evil] in the sight of Allah . And fitnah is greater than killing.” And they will continue to fight you until they turn you back from your religion if they are able. And whoever of you reverts from his religion [to disbelief] and dies while he is a disbeliever – for those, their deeds have become worthless in this world and the Hereafter, and those are the companions of the Fire, they will abide therein eternally.
2:218 Indeed, those who have believed and those who have emigrated and fought in the cause of Allah – those expect the mercy of Allah . And Allah is Forgiving and Merciful.
The words used by God Almighty are clear that the chaos was started and created by the polytheists. The sacred month which Muslims had to abide, and not fight was no longer applicable to them since the polytheists had persecuted the Muslims continually. The wealth of the Muslims were taken. When the Muslims fled to Madinah from persecution, the polytheists still continued oppressing the Muslims. And they had a number of times tried to assassinate the Prophet (p). Giving these factors, what the Companions did in Nakhlah was justified, even though the Prophet (p) never commanded them to do that.
Tafhim al-Qur’an – Sayyid Abul Ala Maududi:
“232 The objection, which was raised in the form of a question about warfare in the sacred month, refers to an incident which took place in the month of Rajab in the second year of Hijra.
The Holy Prophet sent a detachment of eight men to Nakhlah, a place midway between Makkah and Ta’if. He told them to watch the movements of the Quraish and find out their future plans. Though he had not given them permission to fight, they attacked a small trading caravan of the Quraish, killed one than and took the rest prisoners and brought them to Madinah along with their goods.
As this incident took place at a time when it could not be said with certainty whether the month of Rajab had come to an end and the month of Sha’ban had commenced, it was doubtful whether the attack was made in Rajab, a prohibited month, or in Sha’ban. Nevertheless, the Quraish and their secret allies, the Jews, and the double-faced “Muslims” of Madinah, took it as a God-given opportunity to make strong propaganda and raise serious objections against the Believers.
They ironically remarked, “What a pious people they are! They do not hesitate to shed blood even in a prohibited month.” Such objections have been answered in this verse which implies, “No doubt, bloodshed is a very bad thing but their objection is not reasonable, coming as it does from the mouths of those people who themselves had carried on
for thirteen years the most cruel form of persecution against hundreds of their own brethren for no other reason than that they believed in one Allah. They not only forced these brethren of their own to leave their beloved homes but also prevented them from paying a visit to the Ka`bah, although this sacred place was not the property of anyone.
Their crime was all the more heinous because such a wicked antagonism had never existed during the previous two thousand years or so. Therefore those workers of iniquity, the list of whose crimes was so black, had no right to raise objections on the basis of a trivial border incident.
“Moreover, this incident took place without the permission of the Holy Prophet, and was, therefore, nothing more than an’ irresponsible act on the part of a few members of the Islamic party. It should also be kept in view that when this detachment came to the Holy Prophet with the prisoners and the spoils, he said, “I never gave you permission to fight.” He also refused to accept the share due to the public treasury from the spoils.
This clearly showed that it was an unlawful and unauthorised act. The common Muslims also took their men to task for this incident and there was not a single Muslim in the whole of Madinah who approved of this act of theirs.” 
Malik Ghulam Farid:
“260. The believers were told that if disbelievers violated the sanctity of the Sacred Months, they should not hesitate to punish them in the Sacred Months, for thus alone could the sanctity of a sacred thing be safeguarded (2:195). Commentators generally state, and in fact there are traditions to this effect, that on one occasion the Holy Prophet sent Abd’Allah bin Jahsh to bring news about a party of the Quraish proceeding to Mecca. When Abd Allah and his companions reached a place called Nakhlah, they met a small party.
Abd Allah attacked the party killing one of them and capturing two. The date on which this happened was doubtful, some considering it to be one within the sacred Month and others not. The news reached Mecca, the Quraish took advantage of the doubt and protested that the Muslims had violated the sacred Month. The verse under comment was revealed on that occasion.” 
Maulana Muhammad Ali:
“217a. The opening words of this verse prohibit fighting in the sacred months (the reasons for which are given in v. 189), except by way of reprisal (see v. 194). But at the same time the unbelievers are told that the wrongs they inflicted on the Muslims, never caring for the sacred months and the sacred territory, were worse than slaughter.
Then we are told that the unbelievers took up the sword to force the Muslims back into unbelief and that they were determined to carry on the war until they gained this end. Note the words they will not cease fighting you until they turn you back from your religion, if they can, which give the lie direct to the assertion that the Muslims started war to convert the unbelievers by force.
217b. The persons spoken of in this passage are the apostates. A wrong impression exists among non-Muslims, and among many Muslims as well, that the Holy Qur’an requires those who apostatize from Islam to be put to death. This is not true.
One Christian writer has gone so far as to misconstrue the word fa-yamut as meaning he shall be put to death, while even a beginner knows that the significance of these words is then he dies. What is stated here is that the opponents of Islam exerted themselves to their utmost to turn back the Muslims from their faith by their cruel persecutions, and
therefore if a Muslim actually went back to unbelief he would be a loser in this life as well as in the next, because the desertion of Islam would not only deprive him of the spiritual advantages which he could obtain by remaining a Muslim, but also of the physical advantages which must accrue to the Muslims through the ultimate triumph of Islam.
Neither here nor anywhere else in the Holy Qur’an is there even a hint at the infliction of capital or any other punishment on the apostate. The only report which records a case of death being inflicted on apostates is that of the party of ‘Ukl, who, after professing Islam, feigned that the climate of Madinah was insalubrious, and, being told to go
to the place where the herds of camels belonging to the state were grazed, murdered the keepers and drove the herds along with them. The facts of the case clearly show that capital punishment in this case was not inflicted for change of faith, but on account of the crime of murder and dacoity. This case is generally cited by the commentators under 5:33, which speaks of the punishment of dacoits. There is no other case showing that the punishment of death was ever inflicted on apostasy from Islam.
It may, however, be added that after the first eighteen months of their residence at Madinah, the Muslims were in a state of constant warfare with the Qur
aish and the Arab tribes, and apostasy, under these circumstances, meant the desertion of the cause of the Muslims and joining their enemies. Even if death had been prescribed for the apostates, it would have been on the ground of their joining the enemy forces, not on the ground of change of religion. In the matter of religion, the Qur’an gives perfect freedom to everyone to adopt whatever religion he likes: “Say: The Truth is from your Lord; so let him who please believe, and let him who please disbelieve” (18:29).” 
Abdullah Yusuf Ali Tafseer (Commentary):
“237 Prohibited Month; See 2:194, n. 209.
238 The intolerance and persecution of the Pagan clique at Makkah caused untold hardships to the Messenger of Islam and his early disciples. They bore all with meekness and long-suffering patience until the Holy One permitted them to take up arms in self-defence.
Then they were twitted with breach of the custom about Prohibited Months, though they were driven to fight during that period against their own feeling in self-defence. But their enemies not only forced them to engage in actual warfare, but interfered with their conscience, persecuted them and their families, openly insulted and denied Allah, kept out the Muslims from the Sacred Mosque, and exiled them. Such violence and intolerance are deservedly called worse than slaughter.
239 Cf. 2:191, 2:193, where a similar phrase occurs, Fitnah = trial, temptation, as in 2:102; or tumult, sedition, oppression, as here; M.MA., H.G.S., and M.P. translate “persecution” in this passage, which is also legitimate, seeing that persecution is the suppression of some opinion by violence, force, or threats.” 
Tafsir-Ul-Qur’an – Maulana Abdul Majid Daryabadi:
417. (O Prophet!)
418. i.e., Rajab, one of the four months held sacred by the Arabs.
419. (knowingly), i.e., knowing it to be the month of Rajab.
420. (which sin no Muslim has been guilty of). The pagans had charged a certain Muslim with killing a pagan on the 1st of Rajab. The Muslim’s defence, perfectly sound, was that he took the day to be the last date of the preceding month, and did not know that the month of Rajab had commenced.
421. (by subjecting them to the bitterest persecution).
422. (by planting images and idols in the sacred Ka’ba) The words ,,, are grammatically coupled with the pronoun … in .. and not with ….
423. (In a most cruel and heartless way). The pronoun in … refers to … and not to …. The Prophet and the believers alone were competent to dwell with the sacred precincts.
424. (than the accidental slaying of a pagan).
425. (did it lie, then, in the mouth of pagans, who cared neither for the sanctity of the sacred months nor for that of the sacred territory, and respected neither human life nor property, wherever the terrible persecution and unspeakable oppression of the converts to Islam was concerned, to seek refuge in the sanctity of the ‘sacred month?’).
426. (in its effects).
427. (particular and accidental).
428. See nn. 273 and 274 above. So the slaughter that Islam enjoins is to END all slaughter, terrorism, and moral disruption. And there is all the difference in the world between the force that is used to STOP war and the force that is used to make war. But in the words of a present-day Christian writer: “We might as well say that the bludgeon of the policeman and the gun of the gangster are equally criminal.” (A. G. Gardiner)
429. This pictures the furious zeal of anti-Islamic forces of the time. The general war of extermination was certainly organised and started, … It was organised and started by them against Islam.” 
 Sayyid Abul Ala Maududi – Tafhim al-Qur’an – The Meaning of the Qur’an http://www.englishtafsir.com/Quran/2/index.html#sdfootnote232sym
 The Holy Qur’an – Arabic Text With English Translation & Short Commentary  By Malik Ghulam Farid, page 87
 The Holy Quran – Arabic Text with English Translation, Commentary and comprehensive Introduction [Year 2002 Edition] by Maulana Muhammad Ali, Page 96 – 97
 Abdullah Yusuf Ali commentary: http://quranexplained.net/p/Sura-1.html#Sura=2:218&T=1,10,11
 Tafsir -Ul- Qur’an: Translation And Commentary Of the Holy Qur’an [Published by Darul – Isaaht Urdu Bazar Karachi- 1 Pakistan – First Edition 1991] By Maulana Abdul Majid Daryabadi, Volume 1, Page 141