ʿAṭāʾ b. Yasār reports:
A man once came to Ibn ʿAbbās and said, “I proposed to a woman and she refused to marry me, then someone else proposed to her and she wanted to marry him; so I became jealous and killed her. Can I repent from this?” [Ibn ʿAbbās] asked, “Is your mother alive?” He replied, “No.” So he said, “Repent (tawbah) to Allāh the mighty and majestic, and worship him as much as you can.”
ʿAṭāʾ said, “So I went and asked Ibn ʿAbbās, ‘Why did you ask him if his mother was alive?’ He replied, ‘I do not know of any action that brings one closer to Allāh than dutifulness to the mother.'”
Al-Bukhārī, Al-Adab Al-Mufrad ḥadīth 4. Graded ṣaḥīḥ by Al-Albānī. See Ṣaḥīḥ Al-Adab Al-Mufrad, Chapter on Dutifulness to the Mother; Al-Ṣaḥīḥah 6:711 ḥadīth 2799.