Allah the Exalted says:

“Whenever guidance comes to you from Me, then whoever follows My guidance will never go astray nor suffer misery. (123) But whoever turns away from My remembrance will have a constricted life, and on the Day of Resurrection We shall raise him blind. (124) He will say, ‘My Lord, why have You raised me blind when I used to see?’ (125) He will reply, ‘Thus it is: Our signs came to you and you forgot them, and in the same way today you are forgotten.’” (Taha 20:123–126)

Explanation

His words, “fa-immā yaʾtiyannakum” (should guidance come to you), form a conditional clause. Its original wording is in mā, where the particle mā is added for emphasis. The verb of the condition is yaʾtiyannakum (“comes to you”), and its apodosis is the sentence “fa-man ittabaʿa hudāy” (“then whoever follows My guidance”). This latter sentence is itself another conditional clause, so the second condition—with its protasis and apodosis—serves as the response to the first.

Concerning His words, “he will neither go astray nor be miserable,” the meaning is that he will not wander in his knowledge nor be wretched in his deeds. Others say it means he will not go astray in this world nor be miserable in the Hereafter. The two meanings are intimately linked, but it is more common to pair misguidance with knowledge and guidance, and misery with happiness.

As for His saying, “But whoever turns away from My remembrance, for such a one there shall be a constricted life, and We shall raise him on the Day of Resurrection blind” (20:124), some have held that the “constricted life” is the punishment of the grave, where his grave is compressed until his ribs interlock.

Others have said that the constricted life applies to his existence in this world: although outwardly he may seem to enjoy comfort and joy, inwardly his heart is tight and distressed, just as Allah, the Most High, says—