Sahih Bukhari | Volume 5 | Hadith Number 628

Narrated by Salim's father
The Prophet sent Khalid bin Al-Walid to the tribe of Jadhima and Khalid invited them to Islam but they could not express themselves by saying, "Aslamna (i.e. we have embraced Islam)," but they started saying "Saba'na! Saba'na (i.e. we have come out of one religion to another)." Khalid kept on killing (some of) them and taking (some of) them as captives and gave every one of us his Captive. When there came the day then Khalid ordered that each man (i.e. Muslim soldier) should kill his captive, I said, "By Allah, I will not kill my captive, and none of my companions will kill his captive." When we reached the Prophet, we mentioned to him the whole story. On that, the Prophet raised both his hands and said twice, "O Allah! I am free from what Khalid has done."