Abdullah bin Umar reported,

The Prophet ﷺ sent Khalid bin Walid to the tribe of Banu Jadhimah, and he called them to Islam. They did not know how to say, "We have accepted Islam," so they began saying, "Sabana, sabana" (meaning "we have changed our religion"). Khalid then began killing some of them and capturing others, and he handed over a captive to each one of us.When a certain day came, Khalid ordered each of us to kill his captive. I said, "By Allah, I will not kill my captive, nor will any of my companions kill his captive."We went to the Prophet ﷺ and mentioned what had happened. The Prophet ﷺ raised his hands and said, "O Allah, I disassociate myself before You from what Khalid has done," repeating it twice.

Azami 7873

Sahih

عن ابن عمر قال

بعث النبي ﷺ خالد بن الوليد إلى بني جذيمة فدعاهم إلى الإسلام فلم يحسنوا أن يقولوا: أسلمنا، فجعلوا يقولون: صبأنا صبأنا، فجعل خالد يقتل منهم ويأسر، ودفع إلى كل رجل منا أسيره حتى إذا كان يوم، أمر خالد أن يقتل كل رجل منا أسيره، فقلت: والله لا أقتل أسيري، ولا يقتل رجل من أصحابي أسيره حتى قدمنا على النبي ﷺ فذكرناه، فرفع النبي ﷺ يده فقال: اللهم إني أبرأ إليك مما صنع خالد مرتين.

الأعظمي 7873صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Jihad
Chapter
Rulings on jihad and its etiquette
Section
Prohibition of killing one who has declared his Islam
Numbering
Jami al-Kamil 7873 (2nd edition)
Azami 7873