Sahih Bukhari Volume 008, Book 074, Hadith Number 316.
Narated By 'Amr : Ibn 'Umar said, "By Allah, I have not put a brick over a brick (i.e. constructed a building) or planted any date-palm tree since the death of the Prophet." Sufyan (the sub narrator) said, "I told this narration (of Ibn 'Umar) to one of his (Ibn 'Umar's) relatives, and he said, 'By Allah, he did build (something.' "Sufyan added, "I said, 'He must have said (the above narration) before he built."