Musnad Ahmad 1017:93

Waki’ narrated to us, al-A’mash narrated to us, from Sa’d ibn ‘Ubaydah, from Ibn Buraydah, from his father, that he passed by a gathering, and they were speaking against ‘Ali, so he stood over them and said: "There was something in my soul against ‘Ali, and Khalid ibn al-Walid was likewise. The Messenger of Allah (ﷺ) sent me on a military expedition, and ‘Ali was in command of it. We captured some captives." He said: "So ‘Ali took a slave girl from the khums (one-fifth share) for himself. Khalid ibn al-Walid said: 'Take note of this.'" He said: "When we arrived at the Prophet (ﷺ), I began to tell him what had happened, then I said: 'Indeed, ‘Ali took a slave girl from the khums.' And I was a man who kept his head bowed." He said: "So I raised my head, and behold, the face of the Messenger of Allah (ﷺ) had changed, and he said: 'Whoever I am his master (wali), then ‘Ali is his master (wali).'"