"The thing of greatest importance here is the awful fact that, before ever man’s HAND was extended and the transgression committed, that old serpent, the king of the bestial system, the devil, had IMPARTED HIS MIND TO THEM. The MARK OF THE BEAST was in their hearts, in their MINDS, and in their FOREHEADS, and what they did afterward was the MARK OF THE BEAST in their HANDS. It is not difficult to see that the things which men are doing today and have done in ages past are but the MANIFESTATION of that which is in their minds, for, “As a man THINKS in his heart, so is he” (Prov. 23:7) and “a good man out of the good treasure of the heart brings forth good things; and an evil man out of the evil treasure brings forth evil things” (Mat. 12:34-35). The mark of the beast that appears IN THE HAND (outward actions) is the direct result of the mark of the beast IN THE FOREHEAD (mind, nature). This is the mind that inspires the ever increasing confusion and violence that is running rampant among all nations."
In depth study on the mark in the link:
https://www.kingdombiblestudies.org/antichrist/antichrist1.htm#6
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From the link:
"The particular Greek word which has been translated “mark” in Rev. 13:16 is “charagma”, translated eight times as MARK and once as GRAVEN. It is interesting to note that this Greek word for MARK is from the same root from which we get the Greek word CHARAKTER and our English word CHARACTER. In Heb. 1:3 this word is translated as “express image”. “Who being the brightness of His glory, and the EXPRESS IMAGE of His person...” The EXPRESS IMAGE of God is, therefore, the manifestation of God as revealed through His and our CHARACTER. The MARK speaks of that handiwork and the inward thinking which brings forth an expression of character in line with the very source from which the mark comes. Either we will find ourselves expressing the CHARACTER OF GOD, or else the CHARACTER OF THE BEAST. It speaks not, dear ones, of a visible tattoo or brand, nor any outward form which could be pretended for a time, but it refers to that INNER QUALITY OF HIS CHARACTER WHICH IS BEING DEVELOPED IN US, and which in due time shall be revealed."