Praise be to Allaah.  

Islam is the religion of mercy and justice; it commands us to call others to the religion of Allaah in a kind and good manner, and to encourage people to enter this great religion. If some people persist in rejecting the religion of Allaah and stand in the way of ruling by that which Allaah has revealed on earth, or they fight against the call to Allaah, then we give them the choice of three things: 

Either they become Muslim; or if they refuse they pay the jizyah (whereby they pay a specified amount to the Muslims in return for being allowed to remain their land, and the Muslims undertake to protect them); or, if they refuse that, there is nothing left but the way which they themselves have chosen, which is fighting and dealing violently with those who have persecuted the Muslims and put obstacles in the path of the Islamic da’wah. In this way the Muslims will gain the upper hand and the enemies will be humiliated; then when we have killed and wounded many of them and gained the upper hand over them, we may take prisoners and bind a bond firmly on them [cf. Muhammad 47:4], because in that case it is more in tune with the idea of mercy by choice (not because we are afraid of them); at that point war should not continue any longer than is necessary. War in Islam should not be waged for the sole purpose of shedding blood or seeking vengeance. If the Muslims capture them and take them to a place that has been prepared for them, they should not harm them or torture them with beatings, depriving them of food and water, leaving them out in the sun or the cold, burning them with fire, or putting covers over their mouths, ears and eyes and putting them in cages like animals. Rather they should treat them with kindness and mercy, feed them well and encourage them to enter Islam. 

Thumaamah ibn Athaal – the leader of Bani Haneefah – was brought (to Madeenah) as a prisoner and tied to one of the pillars of the mosque. The Messenger (peace and blessings of Allaah be upon him) came to him and said, “What do you think, O Thumaamah?” He said, “What I think, O Muhammad, is good. If you kill me, you will kill one with blood on his hands – i.e., I will deserve to be killed because I have killed Muslims – and if you release me you will release one who will be grateful. If you want money, then ask, and I will give you whatever you want.” The Messenger of Allaah (peace and blessings of Allaah be upon him) left him for three days, and each day he would come and ask him similar questions, and Thumaamah would give similar answers. After the third day, he commanded that he should be released. Thumaamah went to a stand of date-palms near the mosque where he bathed (did ghusl), then he came to the Prophet (peace and blessings of Allaah be upon him) and said, “I bear witness that there is no god except Allaah and I bear witness that Muhammad is the slave of Allaah and His Messenger.” Then he said: “O Messenger of Allaah, by Allaah there was no one on earth whose face was more hateful to me than yours, but now your face is the most beloved of all faces to me.  By Allaah, there was no religion that was more hateful to me than your religion, but now your religion has become the most beloved of all religions to me. By Allaah, there was no land more hateful to me than your land, but now your land has become the most beloved to me. Your cavalry captured me when I was on my way to perform ‘Umrah, so what do you think I should do?” 

The Messenger of Allaah (peace and blessings of Allaah be upon him) congratulated him, and told him to go for ‘Umrah. When he came to Makkah, someone asked him, “Have you changed your religion?” He said, “No, but I have submitted with the Messenger of Allaah (peace and blessings of Allaah be upon him), and by Allaah you will not get a grain of wheat from al-Yamaamah unless the Messenger of Allaah (peace and blessings of Allaah be upon him) gives permission.” 

Think about this story, may Allaah bless you, and how the kind treatment of Thumaamah led to his embracing Islam, which could not have happened were it not primarily by the grace of Allaah, and also the kind treatment which Thumaamah received. 

In the Qur’aan, Allaah says of the righteous (interpretation of the meaning): 

“And they give food, in spite of their love for it (or for the love of Him), to the Miskeen (the poor), the orphan, and the captive,

(Saying): ‘We feed you seeking Allaah’s Countenance only. We wish for no reward, nor thanks from you’”

[al-Insaan 76:8-9] 

Ibn Katheer (may Allaah have mercy on him) said: “Ibn ‘Abbaas said: in those days their prisoners were mushrikeen; on the day of Badr the Messenger of Allaah (peace and blessings of Allaah be upon him) commanded them to be kind to their prisoners, so they used to put them before themselves when it came to food… Mujaahid said, this refers to the one who is detained, i.e., they would give food to these prisoners even though they themselves desired it and loved it.” 

The ruling on tying up prisoners:

 It is well known that if prisoners are able to escape they will not hesitate to do so, because they may be afraid of dying and they do not know what awaits them. Hence the Muslims were commanded to tie up their prisoners and to tie their hands to their necks, lest they run away. This is something that still happens and is well known to all people.

 The wisdom behind permitting the taking of prisoners is so as to weaken the enemy and ward off his evil by keeping him away from the battlefield so that he cannot be effective or play any role; it also creates a means of freeing Muslim prisoners by trading the prisoners whom we are holding.

 Detaining prisoners

 Prisoners should be detained until it is decided what is the best move. The ruler of the Muslims should detain prisoners until he decides what is in the Muslims’ best interests. He may ransom them for money, or exchange them for Muslim prisoners, or release them for nothing in return, or distribute them among the Muslims as slaves, or kill the men, but not the women and children, because the Prophet (peace and blessings of Allaah be upon him) forbade killing the latter. The purpose behind detaining prisoners is so that the Muslims may be protected from their evil. The Prophet (peace and blessings of Allaah be upon him) used to enjoin the Muslims to treat prisoners well, whereas the Romans and those who came before them the Assyrians and Pharaohs, all used to put out their prisoners’ eyes with hot irons, and flay them alive, feeding their skins to dogs, such that the prisoners preferred death to life.

Ahkaam al-Sijn wa’l-Sujana’ wa Mu’aamalat al-Sujana’ fi’l-Islam by Hasan Abi’l-Ghuddah, 256