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

Muhammad Asad

Indeed, [even aforetime] did We send forth Our apostles with all evidence of [this] truth; and through them¹ We bestowed revelation from on high, and [thus gave you] a balance [wherewith to weigh right and wrong], so that men might behave with equity; and We bestowed [upon you] from on high [the ability to make use of] iron, in which there is awesome power as well as [a source of] benefits for man:² and [all this was given to you] so that God might mark out those who would stand up for him and His Apostle,³ even though He [Himself] is beyond the reach of human perception.⁴ Verily, God is powerful, almighty!

Lit., "with them".
Side by side with enabling man to discriminate between right and wrong (which is the innermost purpose of all divine revelation), God has endowed him with the ability to convert to his use the natural resources of his earthly environment. An outstanding symbol of this ability is man's skill, unique among all animated beings, in making tools; and the primary material for all tool-making - and, indeed, for all human technology - is iron: the one metal which is found abundantly on earth, and which can be utilized for beneficial as well as destructive ends. The "awesome power" (ba's shadid) inherent in iron manifests itself not merely in the manufacture of weapons of war but also, more subtly, in man's every-growing tendency to foster the development of an increasingly complicated technology which places the machine in the foreground of all human existence and which, by its inherent - almost irresistible - dynamism, gradually estranges man from all inner connection with nature. This process of growing mechanization, so evident in our modern life, jeopardizes the very structure of human society and, thus, contributes to a gradual dissolution of all moral and spiritual perceptions epitomized in the concept of "divine guidance". It is to warn man of this danger that the Qur'an stresses - symbolically and metonymically - the potential evil (ba's) of "iron" if it is put to wrong use: in other words, the danger of man's allowing his technological ingenuity to run wild and thus to overwhelm his spiritual consciousness and, ultimately, to destroy all possibility of individual and social happiness.
Lit., "those who succour Him and His Apostle", i.e., those who stand up for the cause of God and His Apostle. The meaning is that only they who put God's spiritual and material gifts to right use can be described as "true believers".
See note 3 on 2:3.