Musnad Ahmad 26:260

Hajjaj narrated to us, Sharik informed us, from Simak, from Abd al-Rahman ibn Abd Allah ibn Mas'ud, from his father, from the Prophet, peace and blessings be upon him, who said: "Allah has cursed the consumer of usury, the one who pays it, its two witnesses, and its scribe." He said: And he said: "Usury and adultery do not appear among a people, but that they have made the punishment of Allah, the Mighty and Majestic, permissible for themselves."