Musnad Ahmad 1102:1

Yahya ibn Adam narrated to us, Malik—meaning Ibn Mighwal—narrated to us, he said: I heard Sayyar Abu al-Hakam, more than once, narrating from Shahr ibn Hawshab, from Muhammad ibn Abdullah ibn Salam, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) came to us—meaning Quba—he said: "Allah, the Almighty and Majestic, has praised you well regarding purification, so will you not inform me?" He said: Meaning His saying: {In it are men who love to purify themselves, and Allah loves those who purify themselves} [At-Tawbah: 108]. He said: So they said: "O Messenger of Allah, we find it written for us in the Torah: cleaning with water."