John 17:22-24
Above this passage in my New American Standard Bible, there's a heading, "Their Future Glory." Not to quibble with the writers of that heading (you know I'm going to), I don't think the future glory of God's people is what Jesus is really underlining here.
"Glory" could be seen as the leitmotif of the High Priestly prayer (John 17). It appears eight times in various forms: five times as a verb (glorify and glorified), three times as a noun (glory).
Is Jesus' definitive prayer for His people really that focused on what will happen one day in heaven?
According to Strong's Concordance, "glory" refers to God's splendor and magnificence, or to His incomparable wealth, or to the state of bliss that exists in heaven with Him; "glorify" is a synonym for magnify, greatly honor, or clothe with splendor.
"Glory" doesn't mean heaven, despite how most songwriters use the word. It essentially means God's presence.*
I don't think Jesus is only saying He wants us to behold His glorious presence in heaven, after we die. I think He's also, perhaps mostly, saying He wants His glorious presence to begin transforming us while we're still on earth. When He says (verse 24), "Father, I desire that they...be with Me where I am, so that they may see My glory which You have given Me...," the tenses refer to something present and ongoing, not just to something in the future.
What's the significance for us? Just as the Lord Himself lives in two places, one that's high and exalted and one that's very lowly (us), He wants us to live out our mortal lives in two places -- here on earth and, at the same time, in heaven, where we may behold and be transformed by His magnificent presence.
How does this work? It sounds quite mystical, but in essence I believe it just involves letting Him remove our protective covering -- stop keeping Him out, and He will begin to reveal more of Himself to us.
At the end of verse 24, speaking to the Father, Christ states His reason for wanting us to behold His glory:
"...for You loved Me before the foundation of the world."
If this reason seems slightly illogical, keep reading (verses 25-26):
"O righteous Father, although the world has not known You, yet I have known You; and these have known that You sent Me; and I have made Your name known to them, and will make it known, so that the love with which You loved Me may be in them, and I in them."
It's the ultimate love story.
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*Credit goes to Charles Price for this succinct definition of "glory." Another definition he quite often gives is that the glory of God is the moral character of God.