In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
The questioner asks: Indeed he [i.e. this person] had a disagreement with his father about some wealth and this led him to hate his father, shouted at him and refused to sit with him; so is he sinful for boycotting his father, who is now very old and ill?
Answer: What this son has done to his father is Uqooq [i.e. he’s being undutiful to parents] and it is a major sin, and we seek Allaah’s protection from it. This son [exposes] himself to a great danger and it is obligated on him to repent to Allaah. He should return to his father and make him happy, seek his pardon, seek to please him and honour him. Allaah [The Most High] said: [ وَاعْبُدُوا اللَّهَ وَلَا تُشْرِكُوا بِهِ شَيْئًا ۖ وَبِالْوَالِدَيْنِ إِحْسَانًا – Worship Allah and join none with Him in worship, and do good to parents] [4:36]
And Allaah (Glorified be He and free is He from all imperfections) said: [وَإِن جَاهَدَاكَ عَلَىٰ أَن تُشْرِكَ بِي مَا لَيْسَ لَكَ بِهِ عِلْمٌ فَلَا تُطِعْهُمَا ۖ وَصَاحِبْهُمَا فِي الدُّنْيَا مَعْرُوفًا – But if they (both) strive with you to make you join in worship with Me others that of which you have no knowledge, then obey them not, but behave with them in the world kindl] [31:15] Good behaviour towards parents is required of a person towards his non-Muslim parents, then how about if a person’s parent is a Muslim!
[An Excerpt from ‘Fadaa’il Al-A’maal pages 16-17’ by Shaikh Muhammad Bin Abdillaah As-Subayyil (rahimahullaah). slightly paraphrased]