‘Ali reported Allah's Messenger ﷺ as saying that Gabriel came down to him and said to him, “Give them (i.e. your companions) their choice regarding the prisoners at Badr whether they should be killed or ransomed on condition that a like number of them should be killed the following year.” They replied, “We shall accept ransom and have some of us killed.” Tirmidhi transmitted it, saying this is a gharib tradition.