Early Madinan verse.
47:20 Those who believe say, “Why has a surah not been sent down? But when a precise surah is revealed and fighting is mentioned therein, you see those in whose hearts is hypocrisy looking at you with a look of one overcome by death. And more appropriate for them [would have been]
47:21 Obedience and good words. And when the matter [of fighting] was determined, if they had been true to Allah, it would have been better for them.
Both of these above verses speak about the hypocrites’ behaviour. How when the Muslims are attacked, the hypocrites say when will a verse be sent down by God in order for them to fight? But when verses of fighting did get revealed, these hypocrites would look at each other as if death had taken over them. In reality they didn’t care for the welfare or protection of the Muslims.
Maulana Muhammad Ali:
“20a. The Muslims had been persecuted beyond all measure; they had been oppressed, slain and turned out of their homes. Hence they naturally desired to be allowed to defend themselves. By a chapter is meant a revelation allowing them to fight.
22a. It is the hypocrites who are addressed in these words. Tawallai-tum may mean either that you turn your backs on the Divine commandment to fight in defence of Truth or that you. are put in authority.” 
Dr. Muhammad Asad:
“25 I am rendering the term surah here and in the next sentence as “a revelation”, for whereas there is no surah as such which deals exclusively with questions of war, there are numerous references to it in various surahs; and this is evidently the meaning of this term in the present context as well as in 9::86.
There is no doubt that this verse precedes the revelation, in the year 1 H., of 22:39, which states categorically – and for the first time – that the believers are allowed to wage war whenever “war is wrongfully waged” against them (see in this connection note 57 on 22:39).
26 This is a reference to 22:39-40. For an explanation of the expression muhkamah (“clear in and by itself”), see note 5 on 3:7. (As in the preceding sentence, the term surah has been rendered here, exceptionally, as “revelation”.) 
 The Holy Quran Arabic Text with English Translation, Commentary and comprehensive Introduction by Maulana Muhammad Ali, Page 991
 The Message of The Quran translated and explained by Muhammad Asad, page 1070 – 1071