It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) said:
"There are seventy degrees of usury, the least of which is equivalent to a man having intercourse with his mother." (AR)
English reference (AR): Vol. 3, Book 12, Hadith 2274 (AR)
Arabic reference (AR): Book 12, Hadith 2360 (AR)