Muhammad bin Amr (may Allah have mercy on him) narrates from Abu Salamah bin Abdul Rahman (may Allah have mercy on him), who said: Sayyiduna Mu'awiyah (may Allah be pleased with him) performed Hajj and prayed two rak'ahs. When he went inside, it was said to him: "No one has found fault with your cousin as you have." He said: "What is that?" They said: "You prayed two rak'ahs, whereas Sayyiduna Uthman (may Allah be pleased with him) prayed four." He said: "I prayed two rak'ahs with the Messenger of Allah (peace and blessings be upon him)." They kept pressing him until he went out and prayed four rak'ahs.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16806