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." (ES)
English reference (ES): Vol. 3, Book 12, Hadith 2274 (ES)
Arabic reference (ES): Book 12, Hadith 2360 (ES)