وَأَلْقَىٰ فِي الْأَرْضِ رَوَاسِيَ أَن تَمِيدَ بِكُمْ وَأَنْهَارًا وَسُبُلًا لَّعَلَّكُمْ تَهْتَدُونَ (15)
(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.
*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.