Azwāj is the plural of the word zawj. We need to understand this word as it is the
central point of this surah. It comes from the root zāy wāw jīm which was used for a counterpart, opposite directions (left and right), and for a man and woman. The zawj
of a woman is her husband while the zawj of a man is his wife. The zawj of the moon is the sun and of the sun, the moon.7
Zawj is the other half of something that completes it and forms a complete and
working system with it. Like the male and the female who come together to form a family which is what continues life on earth via offspring, the sun and the moon come together to form a day. Two things, not only different but almost opposites of each other, inherently tied with each other to form a complete and working system. Previously, Allah described the earth as a soft and gentle cradle that sustains life. What is the opposite of being soft? Being firm and solid. Hence, the very next ayah describes the mountains as solid stakes that maintain the balance. When something is soft, it naturally fades and melts away. You need something to hold it together. The softness of the earth refers to its ability to be cultivated and hence produce food which sustains life. The mountains are the pegs that hold this soft earth together and hence act as the zawj of the soft earth. They both come together to form a complete and working system. We know that if the deep roots of the mountains are taken away, it would lead to re-adjustment of the crust. It would cause large scale deformations due to the rise and fall of the surrounding regions as the earth seeks to find balance again.
This is why Allah did not use any verb when describing the mountains as pegs. To imply the necessary existence that would sustain the earth and to establish this relationship between earth and mountains as an indication that this is the theme being carried forward in this surah. From this verse onwards, Allah will continue to mention things with their zawj, except one thing; and that is how Allah will answer the disbelievers.
And created you as azwāj?
Azwāj is the plural of the word zawj. We need to understand this word as it is the
central point of this surah. It comes from the root zāy wāw jīm which was used for a counterpart, opposite directions (left and right), and for a man and woman. The zawj
of a woman is her husband while the zawj of a man is his wife. The zawj of the moon is the sun and of the sun, the moon.7
Zawj is the other half of something that completes it and forms a complete and
working system with it. Like the male and the female who come together to form a family which is what continues life on earth via offspring, the sun and the moon come together to form a day. Two things, not only different but almost opposites of each other, inherently tied with each other to form a complete and working system. Previously, Allah described the earth as a soft and gentle cradle that sustains life. What is the opposite of being soft? Being firm and solid. Hence, the very next ayah describes the mountains as solid stakes that maintain the balance. When something is soft, it naturally fades and melts away. You need something to hold it together. The softness of the earth refers to its ability to be cultivated and hence produce food which sustains life. The mountains are the pegs that hold this soft earth together and hence act as the zawj of the soft earth. They both come together to form a complete and working system. We know that if the deep roots of the mountains are taken away, it would lead to re-adjustment of the crust. It would cause large scale deformations due to the rise and fall of the surrounding regions as the earth seeks to find balance again.
This is why Allah did not use any verb when describing the mountains as pegs. To imply the necessary existence that would sustain the earth and to establish this relationship between earth and mountains as an indication that this is the theme being carried forward in this surah. From this verse onwards, Allah will continue to mention things with their zawj, except one thing; and that is how Allah will answer the disbelievers.
7 Al-Muʿjam al-Ishtiqāqī al-Muʾaṣṣal li-Alfāẓ al-Qurʾān al-Karīm, vol. 2, p. 878