Do sins invalidate the good deeds of one who repents and then returns to sin?

Question:
A person commits sins, but he repents and then returns to them again. He reads the Qur'an and does good, but he persists in returning to those sins. Do these sins invalidate the good deeds he performs?

Answer:
Nothing invalidates good deeds except shirk (associating partners with Allah). It is shirk that invalidates deeds. As for sins less than shirk, they do not invalidate deeds, but their perpetrator sins by them, so he must repent to Allah. If he repents, he should have determination and strength, and not return to the sin a second time. He should not weaken before Satan and before his own self, returning to the sin. Rather, he should resolve and be determined not to return to the sin, seek help from Allah the Mighty and Majestic, and Allah will help him. But if, by chance, he returns to the sin, he should not abandon repentance. He should repent to Allah a second and third time. Every time he sins, it is obligatory for him to repent to Allah the Mighty and Majestic. He should not despair of the mercy of Allah, saying, "Allah will not forgive me, and repentance is of no benefit." This is from Satan. Yes.