Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I think that the Prophet (peace and blessings be upon him) sent Khalid bin al-Walid (may Allah be pleased with him) to Banu Jadhimah, and Khalid invited them to Islam. They could not express themselves well enough to say "We have become Muslims"; instead they said: "We have changed our religion (saba'na)." So Khalid killed some of them and took others captive. He said: Then each man was given his captive, and one morning Sayyiduna Khalid (may Allah be pleased with him) ordered: Kill your captives. Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: I will not kill my captive, nor will any of my companions. Then we came to the Messenger of Allah (peace and blessings be upon him) and mentioned it, and he (peace and blessings be upon him) raised his hands and said: "O Allah, I declare myself free before You of what Khalid has done."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18265