"The idea of God’s glory is often associated with the advent of Jesus. Isaiah promised that “the glory of the Lord shall be revealed” in the day of the Messiah. Angels chorused, “Glory to God in the highest,” at Christ’s birth. The literal meaning of the Hebrew word for glory is “weight” or “substance”. In the eyes of men this literal meaning frequently lent itself to the idea that a person possessing glory was laden (heavy) with the substances of this world. Thus, Jacob’s flock was his “glory” (Gen. 31:1). The Assyrian’s power was their “glory” (Isa. 8:7). Joseph’s high position was his “glory” (Gen. 45:13). But when the word was applied to God it was meant to bring out the weightiness of HIS ATTRIBUTES - His love, justice, righteousness, mercy, power - His CHARACTER. For all that God possesses is simply WHAT HE IS. His “glory” is not what He HAS, but what HE IS. When the glory of the Lord is revealed, the LORD HIMSELF is revealed in all His wonderful nature and character of being. Glory then is not something intangible, or ghostly, or transcendental. If it were this how could Paul ask men to reflect it? Stripped of its physical connotation it is BEAUTY, moral and spiritual beauty, beauty infinitely real, infinitely exalted, yet infinitely near and infinitely communicable."
Much more in the link:
https://www.kingdombiblestudies.org/antichrist/antichrist1.htm#7
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"By far the most impressive truth which underlies the Divine Prescription for perfection is the truth that men are not only mirrors, but that these mirrors, so far from being mere reflectors of the fleeting things they see, transform into their own inmost substance, and hold there in permanent preservation, the things they reflect, for these are not cold, hard mirrors of glass or bronze, but warm, living, impressionable mirrors of spirit, soul, and body. No one knows how the soul can assimilate the things it reflects. But, think of it! the past is not only focused there, in a man’s soul, it IS there. How could it be reflected from there if it were not? All things that he has ever seen, known, felt and believed of the surrounding world are now WITHIN HIM, have become part of him, and ARE HIM - he has been changed into their image. He may deny it, he may resent it, but they are there. They do not adhere to him, they are transfused through him. He cannot alter or rub them out. They are not simply in his memory - they are in HIM. His soul is as they have filled it, made it, left it. These things, these books, these events, these people, these experiences, these influences are his makers. In their hands are his destiny. When once the image or likeness of any of these is truly presented to the soul, no power on earth can hinder two things happening: it must be absorbed into the soul, and forever reflected back again FROM CHARACTER."
"Upon these astounding yet perfectly obvious psychological facts, Paul bases his statement of how men are changed into the image of Christ. “Make Christ your most constant companion” - this is what it practically means for all who treasure the hope of Sonship to God. Live out all your days in intimacy of fellowship and in vital union with HIM. Be more under His influence than under any other influence. Every character has an inward spring, let Christ be it. Every action has a key-note, let Christ set it. Begin every day with the mirror placed at the right angle, turn it towards HIM, and even to your enemy the fashion of your countenance will be changed. Cultivate His friendship. Live after Christ, in His Spirit and in His Word, as in His Presence, and it is difficult to think what more you can do."