Al-Matalib al-'Aliyah 4436 — Reports about the Khawarij

It is narrated from a man of the tribe of Abd al-Qays that he said: I was present (on the battlefield) on the day the people of Nahrawan (the Khawarij) were killed. Then he narrated the complete hadith, in which it is mentioned: If a person's soul could depart (from the body) out of utmost joy and delight, then on that day the soul of Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) would certainly have departed (because of the abundance of joy). At that time he (may Allah be pleased with him) said (about the truth of the event): "Allah and His Messenger (peace and blessings be upon him) have spoken the truth; and whoever told me that he had seen this man (the Khariji with the sign) (alive) among the people before his falling in this place of his death, then I am a liar."
Imam Abu Ya'la recorded it in his Musnad; its chain contains the narrator Abd al-Rahman bin al-Uryan al-Harithi, about whom there is disagreement, but the original incident is supported by other sahih narrations.