Sahih Muslim Book 2, Hadith Number 435.

Chapter : Purification is essential for prayer.

Hammam b. Munabbih who is the brother of Wahb b. Munabbih said: This is what has been transmitted to us by Abu Huraira from Muhammad, the Messenger of Allah (may peace be upon him) and then narrated a Hadith out of them and observed that the Messenger of Allah (may peace be upon him) said: The prayer of none amongst you would be accepted in a state of impurity till he performs ablution.