Allamah Ahmad al-Rumi al-Hanafi (RA) said, “The reality of repentance is that a person seeks forgiveness from Allah Almighty with his tongue and resolves in his heart never to return to that sin. When a person repents in this manner, Allah Almighty forgives his sin, even if it is a very grave sin.”
(Al-Rumi, Ahmad, Majalis al-Abrar wa Masalik al-Akhyar, p. 138, place of publication unknown, n.d.)