Sahih Bukhari Volume 1, Book 12, Hadith Number 793

Narated By ‘Abdullah bin Malik bin Buhaina : Once Allah’s Apostle led us in the Zuhr prayer and got up (after the prostrations of the second Rak’a) although he should have sat (for the Tashah-hud). So at the end of the prayer, he prostrated twice while sitting (prostrations of Sahu).