Sahih Bukhari Volume 8, Book 73, Hadith Number 203.

Narated By ‘Ali : I never heard Allah’s Apostle saying, “Let my father and mother be sacrificed for you,” except for Sa’d (bin Abi Waqqas). I heard him saying, “Throw! (arrows), Let my father and mother be sacrificed for you !” (The sub-narrator added, “I think that was in the battle of Uhud.”)