Quran 9:88 – “But the Messenger, and those who believe with him, strive and fight with their wealth and their persons: for them are (all) good things: and it is they who will prosper.”
The above verse as it so happens often, critics twist, distort the passage, that it endorses violence against the innocent. However, when we examine the verse in its historical context, why it was revealed, it shows that it was the Byzantine (Roman) Empire who had mobilised troops in order to attack the Muslim community 1400 years ago.
What was Prophet Muhammed (p) to do? Sit back and do nothing while the enemy were getting ready to attack Muslims. Prophet Muhammed had done the right thing as he always did, he prepared with his companions to meet the enemy. Three of our early Islamic reports (Hadiths) show that it was the Byzantine (Roman) empire who were the aggressors.
He (Hadrat ‘Umar further) said: I had a companion from the Ansar and, we used to remain in the company of the Messenger (ﷺ) turn by turn. He remained there for a day while I remained there on the other day, and he brought me the news about the revelation and other (matter), and I brought him (the news) like this. And we discussed that the Ghassanids were shoeing the horses in order to attack us.
Id y companion once attended (the Apostle). And then came to me at night and knocked at my door and called me, and I came out to him, and he said: A matter of great importance has happened. I said: What is that? Have the Ghassanids come? He said: No, but even more serious and more significant than that: the Prophet (ﷺ) has divorced his wives. 
Ibn Sa’d’s Kitab al-Tabaqat al-Kabir
“They (narrators) saud: It (report) reached the Messenger of Allah, may Allah bless him, that the Romans had concentrated large forces in Syria, that Heraclius had disbursed one year’s salary to his soldiers, and that tribes of Lakhm, Judham, ‘Amilah and Ghassan had joined hands with him.
They had sent their vanguards to al-Balqa. The Messenger of Allah, may Allah bless him, summoned the people to march. He set out and informed them about the place which he intended, so that they could make necessary preparations. He sent (messengers) to Makkah and to the tribes of Arabia (asking them) to send help. This took place in the days of intense heat.” 
Kitab Futuh Al-Buldan – al-Imam Abu’l Abbas Ahmad Ibn Jabir Al Baladhuri
“Tabuk make terms. When in the year 9 AH the Prophet marched to Tabuk in Syria for the invasion of those of the Greeks, Amilah, Lakhm, Judham and others whom he learnt had assembled against him, he met no resistance. So he spent a few days in Tabuk, whose inhabitants made terms with him agreeing to pay poll-tax.” 
Sayyid Abul Ala Maududi – Tafhim al-Qur’an – The Meaning of the Qur’an
89″…they do not understand anything now,” for they deliberately and intentionally chose the shameful way of staying at home with women, when they were required to go forth for Jihad, though they were healthy, physically fit and well-to-do, and professed Islam. Therefore, according to the Divine Law of Nature. a seal was set upon their hearts and they were bereft of those noble feelings which make one feel ashamed of adopting such a disgraceful conduct. 
 Reference: Sahih Muslim 1479 e, 1475 b In-book reference : Book 18, Hadith 44. USC-MSA web (English) reference: Book 9, Hadith 3511 http://sunnah.com/muslim/18/44″>http://sunnah.com/muslim/18/44
 Ibn Sa’d’s Kitab al-Tabaqat al-Kabir, Translated by S. Moinul Haq (New Delhi: Kitab Bhavan, 2009) Volume 2, 203-204
 The origins of the Islamic State, being a translation from the Arabic accompanied with annotations Geographic and historic notes of the KITAB FUTUH AL-BULDAN of al-Imam Abu’l Abbas Ahmad Ibn Jabir Al Baladhuri, By Phillip Khurti Hitti, PHD, , volume 1, page 92
 Sayyid Abul Ala Maududi – Tafhim al-Qur’an – The Meaning of the Qur’an – http://www.englishtafsir.com/Quran/9/index.html#sdfootnote90sym