Say (0 Muhammad, to the Jews and Christians): "Dispute you with us about Allah while He is our Lord and your Lord? And we are to be rewarded for our deeds and you for your deeds. And we are sincere to Him in worship and obedience (i.e. we worship Him Alone and none else, and we obey His Orders)." Or say you that Abraham, Ishmael, Isaac, Jacob and Al-Asbat (the twelve sons of Jacob) were Jews or Christians? Say. "Do you know better or does Allah (know better . . . that they all were Muslims)? And who is more unjust than he who conceals the testimony i.e. to believe in Prophet Muhammad when he comes, written in their books he has from Allah? And Allah is not unaware of what you do." Surah 2: 130-140
In another surah Almighty Allah declared: 0 People of the Scripture (Jews and Christians)! Why do you dispute about Abraham, while the Torah and the Gospel were not revealed till after him? Have you then no sense? Verily, you are those who have disputed about that of which you have knowledge. Why do you then dispute concerning that which you have no knowledge? It is Allah Who knows, and you know not.
Abraham was neither a Jew nor a Christian, but he was a true Muslim Hanifan (Islamic Monotheism, - to worship none but Allah Alone) and he was not of the polytheists (i.e. he joined none in worship with Allah).
Verily, among mankind who have the best claim to Abraham are those who followed him, and this Prophet (Muhammad) and those who have believed (Muslims). And Allah is the Wali (Protector and Helper) of the believers. Surah 3: 65-68
Allah the Exalted also affirmed: Then, verily! Your Lord - for those who do evil (commit sins and are disobedient to Allah) in ignorance and afterward repent and do righteous deeds, verily, your Lord thereafter, (to such) is Oft-Forgiving, Most Merciful.
Verily, Abraham was an Ummah (a leader having all the good righteous qualities, or a nation), obedient to Allah, Hanifan (i.e. to worship none but Allah), and he was not one of those who were Al-Mushrikeen (polyt heists, idolaters, disbelievers in the Oneness of Allah, and those who joined partners with Allah). (He was) thankful for His (Allah's) Graces. He (Allah) chose him (as an intimate friend) and guided him to a Straight Path (Islamic Monotheism, neither Judaism or Christianity). And We gave him good in this world, and in the Hereafter he shall be of the righteous.
Then, We have inspired you (0 Muhammad saying): "Follow the religion of Abraham Hanifan (Islamic Monotheism - to worship none but Allah) and he was not of the Mushrikeen i.e. polytheists, pagans, idolaters, disbelievers in the Oneness of Allah and in His Messenger Muhammad, those who worship others along with Allah or set up rivals with (or partners to) Allah." Surah 16: 119-123