Sahih Bukhari Volume 003, Book 036, Hadith Number 467.

Narated By Ubai bin Ka'b : Allah's Apostle said, "Both of them (Moses and Al-Khadir) proceeded on till they reached a wall which was about to fall." Sa'd said, "(Al-Khadir pointed) with his hands (towards the wall) and then raised his hands and the wall became straightened up." Ya'la said, "I think Said said, 'He (Khadir) passed his hand over it and it was straightened up." (Moses said to him), "if you had wanted, you could have taken wages for it." Said said, "Wages with which to buy food."