Musannaf Ibn Abi Shayba 4:29

Yazid ibn Harun narrated to us, from Mahdi ibn Maymun, from Muhammad ibn Abi Ya'qub, from Raja' ibn Haywah, from Abu Umamah, who said: I said, "O Messenger of Allah, command me to do a deed by which I may enter Paradise," or something similar to that. He said, "You must fast, for there is nothing equal to it." He (the narrator) said: So Abu Umamah would not be seen with smoke in his house during the day, except when a guest arrived.