Does committing major sins like fornication invalidate one's prayer?

The perpetrator of major sins is in grave danger, for Allah has threatened him with severe torment, as He states: "And whoever does that shall meet the punishment. The torment will be doubled for him on the Day of Resurrection, and he will abide therein in disgrace." He must hasten to repent before it is too late. As for his prayer, it is valid and he is not required to repeat it, but its acceptance depends on piety, "Indeed, Allah accepts only from the righteous." One must beware of deeds being rejected due to sins. And beware of Satan's whisper to abandon prayer due to committing sins, for prayer benefits its performer even with sins; it is an atonement for some of them and a means of exiting the Fire. Thus, preserving it is preserving Islam.