Surely We have sent Our Messengers with Evidence, and We sent down with them the Book and the Balance to keep up the mankind with Justice, and We sent down the Iron, in it has strong power and benefit to the mankind, for knowing to Allah who will help Him and His Messenger unseeingly, indeed Allah is the Powerful, the Exalted.
The Evidence, Book, Balance and Justice mentioned in the verse is Adhikr. Mankind is bestowed with Iron, which is used for several purposes including for weapons of war, is to test them who will utilize it for helping Allah and His Messengers unseeingly, and who will utilize it for mischievous activities in the earth. That means it is given to mankind for identifying who by understanding the aim of life from Adhikr is using it for forming the harmony of mankind as well as peace and tranquility among the mankind, and who is using it for other purposes such as robbery, theft, murder, bloodshed, terrorism, etc. Even though it is told in verse that to identify for Allah who is the Three Time Knower, it is actually for identifying to believer who is the vicegerent of Allah. Such are helping Allah by utilizing Adhikr as the Balance and Trust to keep the universe in its equilibrium, and propagating It to entire mankind to utilize for that purpose. See explanation 9: 67-68; 14: 28-30; 49: 9; and 55: 7-9.