The Book of Prayers (Kitab Al-Salat)

Muslim :: Book 4 : Hadith 782

Abu Huraira reported: A person entered the mosque and said prayer while the Messenger of Allah (may peace be upon him) was sitting in a nook (of the mosque), and the rest of the hadith is the same as mentioned above, but with this addition:" When you get up to pray, perform the ablution completely, and then turn towards the Qibla and recite takbir (Allah o Akbar =Allah is the Most Great)."