The Quran

فَإِذا لَقيتُمُ الَّذينَ كَفَروا فَضَربَ الرِّقابِ حَتّىٰ إِذا أَثخَنتُموهُم فَشُدُّوا الوَثاقَ فَإِمّا مَنًّا بَعدُ وَإِمّا فِداءً حَتّىٰ تَضَعَ الحَربُ أَوزارَها ۚ ذٰلِكَ وَلَو يَشاءُ اللَّهُ لَانتَصَرَ مِنهُم وَلٰكِن لِيَبلُوَ بَعضَكُم بِبَعضٍ ۗ وَالَّذينَ قُتِلوا في سَبيلِ اللَّهِ فَلَن يُضِلَّ أَعمالَهُم

Muhammad Asad

NOW WHEN you meet [in war] those who are bent on denying the truth,¹ smite their necks until you overcome them fully, and then tighten their bonds;² but thereafter [set them free,] either by an act of grace or against ransom, so that the burden of war may be lifted:³ thus [shall it be]. And [know that] had God so willed, He could indeed punish them [Himself]; but [He wills you to struggle] so as to test you [all] by means of one another.⁴ And as for those who are slain in God's cause, never will He let their deeds go to waste:

Sc., "and on barring [others] from the path of God" - thus connecting with verse 1 and laying down the fundamental condition which alone justifies physical warfare: namely, a defence of the Faith and of freedom (cf. in this connection note 167 on 2:190). In other words, when "those who are bent on denying the truth" try to deprive the Muslims of their social and political liberty and thus to. make it impossible for them to live in accordance with the principles of their faith, a just war (jihad) becomes allowable and, more than that, a duty. The whole of the above verse relates to war actually in progress (cf. note 168 on the first part of 2:191); and there is no doubt that it was revealed after 22:39-40, the earliest Qur'anic reference to physical warfare.
Lit., "tighten the bond". According to almost all the commentators, this expression denotes the taking of prisoners of war. In addition, it may also refer to any sanctions or safeguards which would make it unlikely that the aggression could be resumed in the foreseeable future.
Lit., "so that (hatta) the war may lay down its burdens". The term "ransom" comprises also, in this context, a mutual exchange of prisoners of war (Zamakhshari, quoting an opinion of Imam Ash-Shafi'i).
I.e., so as to enable the believers to prove by actual deeds the depth of their faith and their readiness for self-sacrifice, and to enable the aggressors to realize how wrong they have been, and thus to bring them closer to the truth.