We were in the company of the Messenger of Allah (ﷺ) that he observed: Should I not inform you about the most grievous of the grave sins? (The Holy Prophet) repeated it three times, and then said: Associating anyone with Allah, disobedience to parents, false testimony or false utterance. The Prophet was reclining, then he sat up, and he repeated it so many times that we wished that he should become silent.

Associating anyone with Allah, disobedience to parents, killing a person and false utterance.

Avoid the seven noxious things. It was said (by the hearers): What are they, Messenger of Allah? He (the Holy Prophet) replied: Associating anything with Allah, magic, killing of one whom God has declared inviolate without a just cause, consuming the property of an orphan, and consuming of usury, turning back when the army advances, and slandering chaste women who are believers, but unwary.

Abusing one's parents is one of the major sins. They (the hearers) said: Messenger of Allah, does a man abuse his parents too? He (the Holy Prophet) replied: Yes, one abuses the father of another man, who in turn abuses his father. One abuses his mother and he in turn abuses his (the former's) mother.