Abu Dawud Book 36, Hadith Number 4978.

Chapter : Not known.

Narated By Abdullah ibn AbulHamsa’ : I bought something from the Prophet (PBUH) before he received his Prophetic commission, and as there was something still due to him I promised him that I would bring it to him at his place, but I forgot. When I remembered three days later, I went to that place and found him there. He said: You have vexed me, young man. I have been here for three days waiting for you.