God binds himself to time

Christ honoring his Father by becoming a man, stepping into time, and taking on the suffering of this broken world, allowed him to act on his eternal love for the Father in a way he had never done before. He not only demonstrated his love for us as needy and lost rebels but also demonstrated his love for his Father in a new and unique way. 

Not because the Father needed proof of his Son's love, or Christ needed to prove His love for the Father, but so the Son could demonstrate the greatness of his Father and his love for him ¹in a way he had not before. 

We get a hint of the uniqueness of this when we are told that Christ "learned obedience through the things he suffered." - John Piper suggests (and I agree), this was not Christ going from disobedience to obedience, but Christ going from untested obedience to tested obedience - Christ's love for the Father was put to task, if you will, for the first time in a new and unique way. His temptations and choices were very real with real significance. 

It was this same love that moved God to create us, then restore us even after we set aside and abandoned our love and trust in him. 

The love of Christ was so great (for both his Father and us), Christ gave up the preciousness of his full glory and communion with his Father and set it aside (for a ³time) so he might bring others into that same eternal union, communion, and glory he knows and has known from all eternity past. 

And in so doing he now also knows the joy of honoring and pleasing his Father in a way he had not before by seeing this love received and rejoiced in by others (others outside of the Father, Son, and Spirit); a love drawn out of others for his Father, made possible only because of the sacrifice he made. Christ gave up something of that which was most precious to him (the constant, unobstructed, uninterrupted love of his Father) so others might also have it (John 15:11;17:13; Matthew 25:23). And in giving it, he found (finds) great joy (Hebrews 12:2)

As the Father sends me so I send you

  

In the same way that Christ demonstrated his love for the Father by his actions, our showing love by our actions is the clearest way of expressing our love for him and others. Words are important, but actions give evidence of the love we speak of. This is why Christ asked Peter three times to feed his sheep if Peter truly ²loved him. Don't just say you love me, Peter, show me. This is also why we are told that if we love Christ, we will keep his commandments. True love always results in actions.

Before the actual act of the incarnation, love ⁴involving sacrifice by Christ was only a thought that had not been acted out and expressed in the way it was; a thought in the mind of God (as Father, Son, and Spirit) from all eternity past that took place at a specific time in a way it had not occurred before the actual event. There was real action in real-time. Since everything is present to God and known by him this may be hard to fully grasp but is nevertheless clearly what occurred. 

The timeless God for the first time, somehow limited himself in and by time, ⁵entering into and participating in time itself. God for the first and only time, interjected himself into his creation (and specifically toward us, his image-bearers) through Christ and inextricably bound himself to it (us) in love from that point on and for the rest of eternity. Christ has a body he did not have before the incarnation - a ⁶glorified body but a body just the same. A permanent change he willingly partakes in for the honor of His Father and us. 

John 17:5  And now, Father, glorify me in your own presence (again) with the glory that I had with you before the world existed. 

John 17:22  The glory that you have given me I have given to them, that they may be one even as we are one, 

John 17:24  Father, I desire that they also, whom you have given me, may be with me where I am, to see my glory that you have given me because you loved me before the foundation of the world. 

For a fuller discussion on God taking part in creation through the incarnation click here. 
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Footnotes:

¹When love is true it moves one to act on behalf of the one(s) loved.  Acting in love is the completion of it i.e. perfect love is not just a feeling or only words, it is more. It is acting out and upon those feelings. If there is no action there is no true (perfect) love. 

²Christ kept asking Peter regarding agape, not phileo, with which Peter kept responding...

Joh 21:15  So when they had finished breakfast, Jesus said to Simon Peter, "Simon, son of John, do you love G25 Me more than these?" He said to Him, "Yes, Lord; You know that I love G5368 You." He (Jesus) said to him (Peter), "Tend My lambs." 

Jesus asked (3x) "do you agapao me..." 

G25 - ἀγαπάω - agapaō; of unc. or.; to love: - beloved (8), felt a love for (1), love (1), love (75), loved (38), loves (20).

Peter kept answering (also 3x) "You know that I phileo you..."

G5368 - φιλέω - phileō; from G5384; to love:

Thayer Definition:
1) to love
1a) to approve of
1b) to like
1c) sanction
1d) to treat affectionately or kindly, to welcome, befriend
2) to show signs of love
2a) to kiss
3) to be fond of doing
3a) be wont, use to do

³Even though the length of time Christ suffered wasn't eternal, it was infinite i.e. the depth of his suffering made up for the length i.e. it was equivalent to the eternal suffering he spared others from; the extent of his suffering was the equivalent to all suffering throughout eternity for all those who receive him. This was because of the extent of His suffering i.e. losing the infinite wealth and glory of His being for a short time was as great as losing a smaller amount of wealth by a large number of beings for eternity. It had to be in order for His sacrifice to be accepted as a sufficient exchange of life for the death He spared us from. And Christ may experience some loss throughout eternity in being not just God but also a man i.e. he will experience some form of limitation as the God/man that he didn't experience when He was the infinite Son of 

God of all eternity past. Yet he may also experience some kind of gain by being able to continue to participate in creation as a man - albeit a glorified one. 

⁴Possibly this is what is meant by God "knowing good and evil." Because God is not restricted to or by time regarding his knowing all things, in a very significant way (if not in real actual time) he and the Son also knew of the death of the Son prior to it actually happening, while still really and truly participating in this at the time it occurred. We get a hint of this when we are told that Christ "...was slain before the foundation (i.e. creation) of the earth..."

⁵Which tells us how much God values His creation...so much so He gladly took on qualities of creation - i.e. time - to bring to us eternity. This merging of creation with eternity also occurs when God units heaven with earth for all eternity. God loves and values His creation.

Rev 21:1 Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea was no more. 2 And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. 3 And I heard a loud voice from the throne saying, “Behold, the dwelling place of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God. 4 He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning, nor crying, nor pain anymore, for the former things have passed away.”

⁶This is very significant on many levels. One is our new glorified body will be the same glorified body Christ now has. Christ's glorified body allows him to be fully God in a way he was in His pre-incarnated state i.e. His former glory as God the Son has not only been restored but I think we have good reason to think it's also been enhanced. The body Christ now has is the same kind of body we will have. We will never be God but we are like God - in Him image. The significance of this may be far greater than we can now comprehend.