Surat At-Tawbah (113-114)

{مَا كَانَ لِلنَّبِيِّ وَالَّذِينَ آمَنُواْ أَن يَسْتَغْفِرُواْ لِلْمُشْرِكِينَ وَلَوْ كَانُواْ أُوْلِي قُرْبَى مِن بَعْدِ مَا تَبَيَّنَ لَهُمْ أَنَّهُمْ أَصْحَابُ الْجَحِيمِ} (التوبة : 113)

113- It is not proper for the Prophet and those who believed with him to ask for forgiveness for polytheists even if they are their relatives after they had known that they died as disbelievers and they are Hell-dwellers.

The Messenger of Allah (peace be upon him) entered to his uncle Abu Talib while dying and tried to prompt him to say "La Ilaha Illa Allah [No god but Allah]" but he did not until he died while holding fast with the religion of his father `Abdul-Muttalib. Thereupon, the Prophet (peace be upon him) said: "I shall seek forgiveness for you until I am commanded not to do so," thereupon the Ayah was revealed as was reported in Sahih Al Bukhari, Sahih Muslim, and others on the authority of Sa`id ibn Al Musayyib from his father.

However, it is permissible to invoke Allah for live disbelievers with guidance to Islam.

{وَمَا كَانَ اسْتِغْفَارُ إِبْرَاهِيمَ لِأَبِيهِ إِلاَّ عَن مَّوْعِدَةٍ وَعَدَهَا إِيَّاهُ فَلَمَّا تَبَيَّنَ لَهُ أَنَّهُ عَدُوٌّ لِلّهِ تَبَرَّأَ مِنْهُ إِنَّ إِبْرَاهِيمَ لأوَّاهٌ حَلِيمٌ} (التوبة : 114)

114- Abraham's seeking for forgiveness to his father by saying: "And forgive my father for he was from the straying people." [Surat Ash-Shu`ara': 86] was only for guiding him to Islam according to a promise he had given to his father by saying: "I shall seek forgiveness for you." [Surat Al Mumtahinah: 4]. However, when it became clear to Abraham that his father continued his enmity to Allah until he died, he cut the connection between him and his father and gave up his action. Indeed, Abraham was oft-repentant, oft-patient for people's harm, and oft-forgiving.

Muslims used to seek forgiveness for their dead relatives from polytheists under the pretext that Abraham sought forgiveness for his father until the Ayah was revealed to remove any doubt and ambiguity, then they ceased.