Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Sulaiman bin Buraidah (may Allah be pleased with him) that when the Holy Prophet (peace and blessings be upon him) would dispatch an army, he would advise its commander: When you lay siege to a fort and intend to grant them protection in the name of Allah and His Messenger __QUR_N__, do not grant them protection in the name of Allah and His Messenger __QUR_N__, but rather grant them protection in your own name and the name of your forefathers, for it is easier for you to break your own guarantee and that of your forefathers than to break the guarantee of Allah and His Messenger. Hazrat Sufyan (may Allah be pleased with him) says that Hazrat Nu'man bin Muqarrin al-Muzani also narrates in the same manner from the Noble Prophet (peace and blessings be upon him).

Hazrat Abu Wa'il (may Allah be pleased with him) narrates that we were in Khanqin when a noble letter from Hazrat Umar (may Allah be pleased with him) reached us, in which it was written: When you lay siege to a fort and then wish to grant them safety (by offering them amnesty) on Allah's command, do not do so, because you do not know whether you will find Allah's command in this matter or not. Rather, grant them safety and amnesty on your own command, and then afterwards, deal with them as you wish.