Mishkat al-Masabih 3976
Ibn ‘Umar said:
The Prophet sent Khalid b. al-Walid to the B. Hadhima and he summoned them to accept Islam. When they did not express their acceptance of Islam properly but began to say, “We have changed our religion, we have changed our religion,”* Khalid began to kill them and take prisoners, and he handed a prisoner to each one of us. But when a day came when Khalid ordered each of us to kill his prisoner, I said, “I swear by God that I will not kill my prisoner and that not one of my companions will kill his prisoner till we come to the Prophet.” When we mentioned the matter to him he raised his hands and said twice, “O God, I declare myself innocent in Thy sight of what Khalid has done.” 

*Here the verb saba'a is used.

Bukhari transmitted it.
عَنِ ابْنِ عُمَرَ قَالَ: بَعَثَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ خَالِدَ بْنَ الْوَلِيدِ إِلَى بَنِي جَذِيمَةَ فَدَعَاهُمْ إِلَى الْإِسْلَامِ فَلَمْ يُحْسِنُوا أَنْ يَقُولُوا: أَسْلَمْنَا فَجَعَلُوا يَقُولُونَ: صَبَأْنَا صَبَأْنَا فجعلَ خالدٌ يقتلُ ويأسِرُ وَدَفَعَ إِلَى كُلِّ رَجُلٍ مِنَّا أَسِيرَهُ حَتَّى إِذَا كَانَ يَوْمٌ أَمَرَ خَالِدٌ أَنْ يَقْتُلَ كُلُّ رَجُلٍ مِنَّا أَسِيرَهُ فَقُلْتُ: وَاللَّهِ لَا أَقْتُلُ أَسِيرِي وَلَا يَقْتُلُ رَجُلٌ مِنْ أَصْحَابِي أسيره حَتَّى قدمنَا إِلَى النَّبِي صلى الله عَلَيْهِ وَسلم فذكرناهُ فَرَفَعَ يَدَيْهِ فَقَالَ: «اللَّهُمَّ أَنِّي أَبْرَأُ إِلَيْكَ مِمَّا صنعَ خالدٌ» مرَّتينِ. رَوَاهُ البُخَارِيّ