Surah Al-Baqara, Verse 135:
وَقَالُوا كُونُوا هُودًا أَوْ نَصَارَىٰ تَهْتَدُوا قُلْ بَلْ مِلَّةَ إِبْرَاهِيمَ حَنِيفًا وَمَا كَانَ مِنَ الْمُشْرِكِينَ
And they say, "Be Jews or Christians, then you will be guided." Say (to them, O Muhammad Peace be upon him), "Nay, (We follow) only the religion of Ibrahim (Abraham), Hanifa [Islamic Monotheism, i.e. to worship none but Allah (Alone)], and he was not of Al-Mushrikun (those who worshipped others along with Allah – see V. 2:105)."