If a Person Keeps Falling into a Sin He Had Repented From
Ibn Taimiyyah, may Allāh have mercy on him, said:
It is not allowed for a Muslim, if he were to repent and then afterwards go back [to committing the sin], to persist [on that sin]; rather, he [must] repent, even if he were to go back [to that sin] a hundred times in a day.
Majmūʿ Al-Fatāwá, vol. 16, p. 58.
N.B.: Title mine (Tr.)
Translated by Mikail ibn Mahboob Ariff