"And We cast therein firm mountains"—the firm mountains (rawasi) are the mountains with which He stabilized the earth. "And We caused to grow therein from every beautiful pair"—meaning: beautiful, and everything that grows on the earth, each of its types is a pair.
﴿وألقينا فِيهَا رواسي﴾ الرواسِي: الْجبَال أَثْبَتَ بهَا الأرضَ ﴿وَأَنْبَتْنَا فِيهَا مِنْ كُلِّ زَوْجٍ بهيج﴾ حسن، وكل مَا ينْبت فِي الأَرْض فالواحد مِنْهُ زوج