The Quran

لَقَد أَرسَلنا رُسُلَنا بِالبَيِّناتِ وَأَنزَلنا مَعَهُمُ الكِتابَ وَالميزانَ لِيَقومَ النّاسُ بِالقِسطِ ۖ وَأَنزَلنَا الحَديدَ فيهِ بَأسٌ شَديدٌ وَمَنافِعُ لِلنّاسِ وَلِيَعلَمَ اللَّهُ مَن يَنصُرُهُ وَرُسُلَهُ بِالغَيبِ ۚ إِنَّ اللَّهَ قَوِيٌّ عَزيزٌ

Ali Unal

Assuredly We have sent Our Messengers with manifest truths (and clear proofs of their being Messengers), and We have sent down with them the Book and the Balance so that (relations among) humankind may live by equity. And We have sent down iron,¹ in which is stern might and benefits for humankind, so that God may mark out those who help (the cause of) God and His Messengers, though they do not see Him. Surely God is All-Strong, All-Glorious with irresistible might.²

Sending down iron means the same as sending down cattle in 39: 6; iron is one of God’s great bounties which He has bestowed out of the treasures He has with Him, as stated in 15: 21: There is not a thing but the stores (for its life and sustenance) are with Us, and We do not send it down except in due, determined measure.
Iron is perhaps the most important and necessary matter for technology. It is also our most elemental material, as it is the core of the earth. So, this verse may also be referring to the origins of the earth. Iron is also necessary to make weapons to fight in God’s cause to uphold His Word, and to eradicate injustice.
From another point of view, this verse is very significant in assessing a sound society and government. The Messengers are the God-appointed leaders of humankind, who always guided them to the truth and led them in all aspects of life throughout human history. The Book is the compilation of knowledge, instructions, and laws essential to their happiness in both worlds. The Balance is the criterion to attain what is right in belief, thinking, and action, and also to realize justice in human individual and social life (see sūrah 55: 7–9, note 4). Iron symbolizes force or power in human social life. Without the Book, iron (force) destroys justice and brings about injustice. Without the Balance, iron misuses the Book according to its own benefits. Without iron, the Book and Balance are not sufficient to form a good society and government. Said Nursi remarks: “Principles of wisdom and laws of truth have no effect upon ordinary people unless the former are combined with the state’s laws and the latter with power” (The Letters, “Seeds of the Truth,” 2: 306).