﴿ فَذَٰلِكُمُ ٱللَّهُ رَبُّكُمُ ٱلْحَقُّ ۖ فَمَاذَا بَعْدَ ٱلْحَقِّ إِلَّا ٱلضَّلَٰلُ ۖ فَأَنَّىٰ تُصْرَفُونَ ﴾

“seeing that He is God, your Sustainer, the Ultimate Truth? For, after the truth [has been forsaken], what is there [left] but error? How, then, can you lose sight of the truth?"”

That Doer of all these things then is God your true established Lord so what is there after truth except error? the interrogative is meant as an affirmative in other words there is nothing after it truth other than that error; thus he who mistakes the truth which is the worship of God has fallen into error. How then are you turned away from faith despite the proofs having been established?