There is no deed closer to Allah than this one!

In a report that was classed as saheeh by al-Albaani in Saheeh al-Adab, from Atta' ibn Yassar that Ibn ‘Abbaas (may Allaah be pleased with them) said that a man came to him and said: I proposed marriage to a woman but she refused to marry me; someone else proposed to her and she agreed to marry him. I got jealous and killed her. Can I repent? He said: Is your mother alive? He said: No. He said: Repent to Allah, may He be glorified and exalted, and seek to draw near to Him as much as you can (by doing good deeds). I went and asked Ibn ‘Abbaas: Why did you ask him if his mother was alive? He said: Because I do not know of any deed that will bring one closer to Allah, may He be glorified and exalted, than honoring one’s mother.

Sahih al-Adab al-Mufrad