Surat Al Baqarah (132-133)

{ وَوَصَّى بِهَا إِبْرَاهِيمُ بَنِيهِ وَيَعْقُوبُ يَا بَنِيَّ إِنَّ اللّهَ اصْطَفَى لَكُمُ الدِّينَ فَلاَ تَمُوتُنَّ إَلاَّ وَأَنتُم مُّسْلِمُونَ } [البقرة:  132]

132- Abraham, the Khalil (the closest chosen Prophet by Allah), enjoined his sons with this religion [i.e., Islam] saying: O my sons, the religion which Allah had chosen for you is the best religion. There is no other religion accepted but Islam, so be firm on it and do not turn away therefrom. Be keen to be on Islam until death by doing goodness in this life, obedience to Allah and good deeds. A person usually dies on the religion he used to adopt during his lifetime as he shall be resurrected on that either. Those who intend to do good, Islam will be easy for them and whoever intends good, Allah will make him firm on that.

{ أَمْ كُنتُمْ شُهَدَاء إِذْ حَضَرَ يَعْقُوبَ الْمَوْتُ إِذْ قَالَ لِبَنِيهِ مَا تَعْبُدُونَ مِن بَعْدِي قَالُواْ نَعْبُدُ إِلَـهَكَ وَإِلَـهَ آبَائِكَ إِبْرَاهِيمَ وَإِسْمَاعِيلَ وَإِسْحَاقَ إِلَـهاً وَاحِداً وَنَحْنُ لَهُ مُسْلِمُونَ } [البقرة:  133]

133- Or were you witnesses, O Pagans and the People of the Scriptures, over what Jacob (peace be upon him) said to his sons when death approached him: What will you worship after my death? He wanted his sons to confess the Oneness of Allah, adhere to Islam and to take their covenant to be firm on that.
They said as their father wished: We shall worship Allah Whose Presence and Deity are confirmed; the god whom you, Abraham, Ishmael and Isaac worship. He is the One, whom we worship alone without partners; we are obedient and submissive to Him.
Islam is the religion of all Prophets, even if their legislations were varied.
The Qur'an counted Ishmael of the forefathers of Jacob as he was the uncle of Jacob (peace be upon him).