مَدَدْنَا (Madadnaa) is from مَدَّ (Madda) which means to lay out flat.
وَالْأَرْضَ مَدَدْنَاهَا وَأَلْقَيْنَا فِيهَا رَوَاسِيَ وَأَنبَتْنَا فِيهَا مِن كُلِّ زَوْجٍ بَهِيجٍ
“And the earth, We have spread it out and We cast in it anchors (firmly set mountains) and We made grow within it [something] of every beautiful kind”.
Language points
رَوَاسِيَ (Rawaasiy) comes from رَسَا (Rasaa) which means “to anchor”. It is used to refer to mountains as fixtures that are firmly established and don’t move.
زَوْجٍ (Zawj) – In addition to referring to “a pair” in Arabic, it is also used to refer to “a kind” or “species” of something. A grouping of things that complement each other are known as a زَوْجٍ (Zawj).
For example, in Surah Al-Waaqi’ah Allah says: وَكُنتُمْ أَزْوَاجًا ثَلَاثَةً “And you were three groups” i.e., groups of people with three different descriptions and realities.
بَهِيجٍ (Baheej) comes from the word بَهْجَة (Bahjah) that covers the meaning of “joy and delight” and the meaning of “splendour and beauty”. بَهِيجٍ (Baheej) captures the meaning of something being so beautiful that it brings you joy.
Insights
Comparisons can be drawn between this verse about the earth and the prior verse about the sky. The sky is described as being above you whilst the earth is laid out below us.
He spoke about beautifying the sky whilst describing how mountains were firmly placed on the earth which are a demonstration of the beauty of the earth.
Then He states that the sky does not have any rifts or ruptures (Furooj) whilst in contrast the earth has been planted with all kinds of plants and every kind of vegetational growth which fill the gaps or ruptures found on the earth.
The sky is beautiful because it has no cracks or holes whilst the earth is beautiful because it fills its holes with that which has colour and beauty.
In this way the two verses are beautifully balanced with each other.