6 : 149
قُلۡ فَلِلَّهِ ٱلۡحُجَّةُ ٱلۡبَٰلِغَةُۖ فَلَوۡ شَآءَ لَهَدَىٰكُمۡ أَجۡمَعِينَ
Say, "With Allāh is the far-reaching [i.e., conclusive] argument. If He had willed, He would have guided you all."
Ayah 149 of الأنعَام (6 : 149). This page carries the verse in the Uthmani script with a translation of its meaning, at a stable URL that can be cited on its own.
قُلۡ فَلِلَّهِ ٱلۡحُجَّةُ ٱلۡبَٰلِغَةُۖ فَلَوۡ شَآءَ لَهَدَىٰكُمۡ أَجۡمَعِينَ
Say, "With Allāh is the far-reaching [i.e., conclusive] argument. If He had willed, He would have guided you all."