Musnad Ahmad 26:178

Muhammad narrated to us, Shu'bah narrated to us, from Simak ibn Harb, he said: I heard 'Abd al-Rahman ibn 'Abd Allah narrating from 'Abd Allah ibn Mas'ud, that he said: "Two bargains in one bargain are not valid." And indeed, the Messenger of Allah (peace and blessings of Allah be upon him) said: "Allah has cursed the consumer of usury, the one who pays it, its witness, and its scribe."