Musnad Abu Ya'la al-Mawsili 152:157

Abu Khaythama narrated to us, Abdullah ibn Idris narrated to us, al-Hasan ibn Ubayd Allah narrated to us, from Ibrahim, who said: Alqama led us in prayer and prayed five [rak'ahs]. The people whispered and criticized him. I said, "You have done [that]." He said, "And you, one-eyed one, are saying that?" He said: Then he turned away and performed two prostrations. Then he narrated to them from Abdullah that the Prophet (peace and blessings of Allah be upon him) prayed five [rak'ahs] with them. It was said to him regarding that, so he turned away and performed two prostrations and said, "I am only a human being; I forget just as you forget."