The Prophet (ﷺ) said: "Usury has seventy-three categories, the least one in sin is as that of a man who marries (has sexual relations with) his mother, and the very essence of usury is the (violation of the) honor of a Muslim man." [Ibn Majah reported it in a short form and al-Hakim in a complete one. The latter also graded it Sahih (authentic)].