ثُمَّ بَدَّلْنَا مَكَانَ ٱلسَّيِّئَةِ ٱلْحَسَنَةَ حَتَّىٰ عَفَوا۟ وَّقَالُوا۟ قَدْ مَسَّ ءَابَآءَنَا ٱلضَّرَّآءُ وَٱلسَّرَّآءُ فَأَخَذْنَٰهُم بَغْتَةً وَهُمْ لَا يَشْعُرُونَ
Important Words:
عفوا (they grew) is derived from عفا which gives a number of meanings: (1) it was or became effaced or obliterated; (2) transitively, he or it effaced or obliterated something; (3) he forgave or pardoned; (4) it was or became much in quantity or many in number; or (5) transitively, he made it much in quantity or many in number, etc. (Lane).
Commentary:
The words حسنة (good condition) and سیئة (evil condition) are not used here in their moral sense, but in the sense of straitness and plenty.
It is invariably the case that when the afflictions and miseries which come upon a disbelieving people as a result of their rejection of a Prophet of God pass away and ease and comfort take their place, then instead of improving their condition and turning to God in repentance, they refuse to recognize past afflictions as heavenly visitations and as signs of the truth of their Prophet, but, on the contrary, begin to say that they were merely normal occurrences of nature which even their forefathers experienced in their time but which then passed away.