وَلَا تَمْشِ فِى ٱلْأَرْضِ مَرَحًا ۖ إِنَّكَ لَن تَخْرِقَ ٱلْأَرْضَ وَلَن تَبْلُغَ ٱلْجِبَالَ طُولًا
Wa laa tamshi fil ardi marahan innaka lan takhriqal arda wa lan tablughal jibaala toola
Do not strut arrogantly about the earth: you cannot break it open, nor match the mountains in height.
And do not walk the earth in arrogance — you will never tear it open, nor reach the mountains in height.
The answer to swagger here is measurement: a person walks between ground they cannot split and peaks they cannot match, and those two limits are the whole of the argument. Maraḥ is gladness that has spilled into strut rather than pride in the abstract, which is why the correction is physical instead of moral. The same clause is put in Luqman's mouth as counsel to his son at 31:18, and here it closes the list that verse 39 calls wisdom.