Musnad Ahmad 31:343

Abu Abd al-Rahman Abdullah ibn Yazid al-Muqri narrated to us, Haywah and Ibn Lahi'ah narrated to us, they said: Salim ibn Ghaylan al-Tujibi informed us that he heard Darraj Abu al-Samh saying that he heard Abu al-Haytham saying that he heard Abu Sa'id al-Khudri saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "I seek refuge in Allah from disbelief and debt." A man said: "O Messenger of Allah, is debt equated with disbelief?" The Messenger of Allah, peace and blessings of Allah be upon him, said: "Yes."