ءَاتُونِى زُبَرَ ٱلْحَدِيدِ ۖ حَتَّىٰٓ إِذَا سَاوَىٰ بَيْنَ ٱلصَّدَفَيْنِ قَالَ ٱنفُخُوا۟ ۖ حَتَّىٰٓ إِذَا جَعَلَهُۥ نَارًا قَالَ ءَاتُونِىٓ أُفْرِغْ عَلَيْهِ قِطْرًا
Commentary:
In addition to human labour Cyrus demanded iron and molten copper from the inhabitants of the place. Copper, unlike iron, does not rust and when it is mixed with iron the mixture becomes all the more hard and defies rusting and corrosion. In order to keep the pass open for traders and commercial travellers Cyrus wanted to construct gates in the wall and for that purpose he required iron and molten copper.
In addition to human labour Cyrus demanded iron and molten copper from the local people. Copper, unlike iron, does not rust and when it is mixed with iron the mixture becomes harder still and defies rusting and corrosion. The engineering and technical skill were supplied by the technicians of Cyrus.
The rampart was built between the Caspian Sea and the Caucasus range.