Reference: Siyar A’laam an-Nubalaa – Volume 6, Page 376
al-Falaas said: I heard Ibn Abee ‘Adee say:
Daawood ibn Abee Hind fasted [voluntary fasts] for forty years, and his family were not aware of it. He was very discrete, and would take his [packed] lunch with him, and then give it away [to someone needy] along the way.