Musannaf Ibn Abi Shayba 1:2084

Waki’ and Humayd narrated to us, from al-A’mash, from ‘Amr ibn Murrah, from ‘Abdullah ibn Salamah, who said: ‘Ali said to me: "I perform ghusl on a cold night, without being in a state of janabah, in order to strengthen myself and to purify myself."