Musnad Ahmad 1034:203

'Amr ibn 'Asim narrated to us, from Hammad ibn Salamah, from 'Ali ibn Zayd, from al-Hasan, from Jundub, from Hudhayfah, from the Prophet, peace and blessings of Allah be upon him, who said: "It is not appropriate for a Muslim to humiliate himself." It was said: "And how does he humiliate himself?" He said: "He exposes himself to a trial that he cannot bear."