Tawhid (Monotheism) - the absolute oneness of Allah

إِنَّ هَـٰذَا لَهُوَ ٱلْقَصَصُ ٱلْحَقُّ ۚ وَمَا مِنْ إِلَـٰهٍ إِلَّا ٱللَّهُ ۚ وَإِنَّ ٱللَّهَ لَهُوَ ٱلْعَزِيزُ ٱلْحَكِيمُ

Indeed, this is the true narration. And there is no deity except Allāh. And indeed, Allāh is the Exalted in Might, the Wise.

يَـٰٓأَهْلَ ٱلْكِتَـٰبِ لَا تَغْلُوا۟ فِى دِينِكُمْ وَلَا تَقُولُوا۟ عَلَى ٱللَّهِ إِلَّا ٱلْحَقَّ ۚ إِنَّمَا ٱلْمَسِيحُ عِيسَى ٱبْنُ مَرْيَمَ رَسُولُ ٱللَّهِ وَكَلِمَتُهُۥٓ أَلْقَىٰهَآ إِلَىٰ مَرْيَمَ وَرُوحٌ مِّنْهُ ۖ فَـَٔامِنُوا۟ بِٱللَّهِ وَرُسُلِهِۦ ۖ وَلَا تَقُولُوا۟ ثَلَـٰثَةٌ ۚ ٱنتَهُوا۟ خَيْرًا لَّكُمْ ۚ إِنَّمَا ٱللَّهُ إِلَـٰهٌ وَٰحِدٌ ۖ سُبْحَـٰنَهُۥٓ أَن يَكُونَ لَهُۥ وَلَدٌ ۘ لَّهُۥ مَا فِى ٱلسَّمَـٰوَٰتِ وَمَا فِى ٱلْأَرْضِ ۗ وَكَفَىٰ بِٱللَّهِ وَكِيلًا

O People of the Scripture, do not commit excess in your religion or say about Allāh except the truth. The Messiah, Jesus the son of Mary, was but a messenger of Allāh and His word which He directed to Mary and a soul [created at a command] from Him. So believe in Allāh and His messengers. And do not say, "Three"; desist - it is better for you. Indeed, Allāh is but one God. Exalted is He above having a son. To Him belongs whatever is in the heavens and whatever is on the earth. And sufficient is Allāh as Disposer of affairs.