Musannaf Ibn Abi Shayba 1:756

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Sa‘id, from Qatadah, from Muslim ibn Yasar, from Humran: That ‘Uthman, when he would perform ghusl (full-body ablution) for janabah (major ritual impurity) and would exit his place of bathing, he would wash the soles of his feet. He said: And Muslim said, "I do not mind if I exit from my place of bathing to my place of prayer."