Tawhīd (monotheism) as the core message of all prophets

فَأَرْسَلْنَا فِيهِمْ رَسُولًا مِّنْهُمْ أَنِ ٱعْبُدُوا۟ ٱللَّهَ مَا لَكُم مِّنْ إِلَـٰهٍ غَيْرُهُۥٓ ۖ أَفَلَا تَتَّقُونَ

And We sent among them a messenger from themselves, [saying], "Worship Allāh; you have no deity other than Him; then will you not fear Him?"