Sahih Muslim Book 3, Hadith Number 640.

Chapter : The desirability of pouring water thrice on the head and other parts (of the body).

Jabir b. Abdullah reported: A delegation of the Thaqif said to the Apostle of Allah (may peace be upon him): Our land is cold; what about our bathing then? He (the Holy Prophet) said: I pour water thrice over my head.