Musnad Ahmad 33:635

Musa narrated to us, Ibn Lahi'ah narrated to us, from Abu al-Zubayr, who said: I asked Jabir about the ghusl (ritual bath). Jabir said: The tribe of Thaqif came to the Prophet, peace and blessings of Allah be upon him, and said: "Our land is a cold land, so how do you command us regarding the ghusl?" The Prophet, peace and blessings of Allah be upon him, said: "As for me, I pour [water] over my head three times." And he did not say anything other than that.