أَوَلَمْ يَسِيرُوا فِي الْأَرْضِ فَيَنْظُرُوا كَيْفَ كَانَ عَاقِبَةُ الَّذِينَ مِنْ قَبْلِهِمْ وَكَانُوا أَشَدَّ مِنْهُمْ قُوَّةً وَمَا كَانَ اللَّهُ لِيُعْجِزَهُ مِنْ شَيْءٍ فِي السَّمَاوَاتِ وَلَا فِي الْأَرْضِ إِنَّهُ كَانَ عَلِيمًا قَدِيرًا ﴿۴۴﴾ وَلَوْ يُؤَاخِذُ اللَّهُ النَّاسَ بِمَا كَسَبُوا مَا تَرَكَ عَلَى ظَهْرِهَا مِنْ دَابَّةٍ وَلَكِنْ يُؤَخِّرُهُمْ إِلَى أَجَلٍ مُسَمًّى فَإِذَا جَاءَ أَجَلُهُمْ فَإِنَّ اللَّهَ كَانَ بِعِبَادِهِ بَصِيرًا ﴿۴۵﴾

﴾44﴿ Awalam yaseeroo fil ardi fa yanzuroo kaifa kaana 'aaqibatul lazeena min Qablihim wa kaanoo ashadda minhum quwwah; wa maa kaanal laahu liyu'jizahoo min shai'in fis samaawaati wa laa fil ard; innahoo kaana 'Aleeman Qadeeraa
﴾45﴿ Wa law yu'aakhizul laahun naasa bima kasaboo maa taraka 'alaa zahrihaa min daaabbatinw wa laakiny yu'akhkhiruhum ilaaa ajalim musamman fa izaa jaaa'a ajaluhum fa innal laaha kaana bi'ibaadihee Baseeraa

﴾44﴿ Have they not traveled through the land and seen how the end of those before them was, They were stronger than them in power. And nothing in the heavens or the earth can escape Allah's control. Indeed, Allah is All-Knowing, All-Powerful
﴾45﴿ And if Allah Almighty were to take people to account for what they have done, He would not leave a single living creature on the surface of the earth. But He grants them respite until a specified time. Then, when their appointed time comes, indeed, Allah is All-Seeing of His servants

[44] This too is a worldly warning.
After mentioning the way (sunnah) of the former nations, the method of drawing lessons from it is mentioned—namely, through traveling and observing (i.e., reflecting on the ruins and fates of past nations).
It gives a clear reminder that no one can oppose or resist Allah the Exalted in any way.
[45] This too falls under worldly warning (تخویف دنیوی).
Since the deniers would hastily demand the punishment, this verse responds to them.
"النَّاسَ" refers to sinful people—whether they are believers or polytheists.
"بِمَا كَسَبُوا" means due to all their sins, not a single one of which is excused for them.
And what is meant by "all" is that due to certain sins, certain punishments descend in this world—as mentioned in Surah Ar-Rum (30:41).
"مَا تَرَكَ عَلَى ظَهْرِهَا"—humans reside on different parts of the earth, and this is likened to a rider mounted on the back of a mount (animal), hence the term "ظَهْرِهَا" (its back) is used for the earth.