What did Ibn `Umar do to honor the legacy of the Prophet Muhammad (saw) after his death?
 Narrated `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."