And He has cast into the earth firmly set mountains, lest it (16:15)

Almuntakhab Fi Tafsir Alquran Alkarim

And the earth He furnished with firm stays (mountains) placed in a certain setting, fixed as with an anchor to stabilize* it lest it should sway you from side to side or in all directions. And He furnished it with rivers and road-ways to use as a guide in your travels from one place to another

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(16:15) He has driven mountains firmly into the earth lest it should turn away from its usual course along with you: *12 He has caused rivers to flow and made natural ways *13 so that you may be directed aright.

And He has cast into the earth firmly set mountains, lest it meaning

*12) This shows that the real function of mountains is to regulate the motion and speed of the Earth. We have come to this conclusion, for the Qur'an has made this benefit of mountains very prominent in many places. Therefore, their other benefits should be regarded as incidental.
*13) Natural ways are those routes which are formed along the banks of streams, ravines and rivers. Though the importance of these ways is great even in the plains, one feels their sore need, especially in the mountainous regions.
 

And He has cast into the earth firmly set mountains, lest it meaning in Urdu

اُس نے زمین میں پہاڑوں کی میخیں گاڑ دیں تاکہ زمین تم کو لے کر ڈھلک نہ جائے اس نے د ریا جاری کیے اور قدرتی راستے بنائے تاکہ تم ہدایت پاؤ