The Quran

وَلا تُعجِبكَ أَموالُهُم وَأَولادُهُم ۚ إِنَّما يُريدُ اللَّهُ أَن يُعَذِّبَهُم بِها فِي الدُّنيا وَتَزهَقَ أَنفُسُهُم وَهُم كافِرونَ

Muhammad Asad

And let not their worldly goods and [the happiness which they may derive from] their children excite thy admiration: God but wants to chastise them by these means in [the life of] this world, and [to cause] their souls to depart while they are [still] denying the truth.¹

Cf. 3 : 178 and 8:28, as well as the corresponding notes. This (almost literal) repetition of verse 55 above is meant to stress the psychological importance of this problem (Zamakhshari) - namely, the insignificance of worldly happiness as compared with spiritual righteousness or the absence of it.