Abu Dawud Book 25, Hadith Number 3973.

Narated By Ubayy ibn Ka’b : When the Apostle of Allah (PBUH) prayed, he began with himself and said: May the mercy of Allah be upon us and upon Moses. If he had patience, he would have seen marvels from his Companion. But he said: “(Moses) said: If ever I ask thee about anything after this, keep me not in they company: then wouldst thou have received (full) excuse from my side”. Hamzah lengthened it.