Sayyiduna Abdullah bin Hanzalah (may Allah be pleased with him), whose father was washed by the angels, narrates: The Prophet (peace and blessings be upon him) said: "A single dirham of usury (riba) that a man consumes knowingly is worse (a greater sin) than committing fornication thirty-six times."
Ahmad and al-Tabarani in al-Mu'jam al-Kabir and al-Mu'jam al-Awsat recorded it; Ahmad's narrators are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6573