In the Orthodox understanding of salvation, we see the entirety of the life of Christ to be all for our salvation. St. Paul beautifully expresses this fullness in Ephesians, chapter 2. He says:
'' 4 But God, who is rich in mercy, because of His great love with which He loved us, 5 even when we were dead in trespasses, made us alive together with Christ (by grace you have been saved), 6 and raised us up together, and made us sit together in the heavenly places in Christ Jesus...'' (Ephesians 2:4-6)
That's Ephesians 2:4-6. In that last part, he speaks of raising us up with Him and we know this to be true and effected through His resurrection. But it doesn't end there: our salvation is total and complete. St. Paul says that He has made us sit together in the heavenly places in Christ Jesus. His Ascension is our ascension. We are seated with Him in the heavenly places. In Him, even now, we have access to the heavenly places because of His Ascension.
An important part of our salvation is to restore us to a heavenly culture, a spiritual way of being, for our citizenship is no longer on earth, but as St. Paul says, our citizenship is in Heaven. Look at how St. Paul puts it in Colossians, chapter 3:
'' 1 Therefore since you have been raised with Christ, strive for the things above, where Christ is seated at the right hand of God. 2 Set your mind(s) on things above, not on earthly things. 3 For you died, and your life is now hidden with Christ in God. 4 When Christ, who is your life, appears, then you also will appear with Him in glory.'' (Colossians 3:1-4) - [Berean Standard Bible]
Our very life is hidden with Christ in God. Why? And how? Well, the answer is simple: it is through His Ascension. His salvific work restores everything that was lost to us. Not only has He healed us, not only has He brought us from death to life, but He also returns us into the heavenly places in the very presence of His Father and our Father. And how does this happen? It's through His Ascension.
The truth is that the Son is always in the presence of the Father, even while He was on earth. And so the Ascension was for our sake. This is how St. Cyril speaks of the Ascension:
''For Christ has not ascended in order to make his own appearance before God the Father. (...) he has done this on our account and in our name, so that being like us,
though with his power as the Son, and hearing the command, ''Sit at my right hand,'' as a member of our race, he might transmit to all of us the glory of being children of God. For since he became man it is as one of us that he sits at the right hand of God the Father, even though he is above all creation and one in substance with his Father, having truly come forth from him as God from God and Light from Light.
''As man then he appeared before [God] the Father on our behalf, to enable us whom the ancient transgression had excluded from his presence once more to see the Father's face. As the Son he took his seat to enable us as sons and daughters through him to be called children of God. So Paul, who claims to speak for Christ, teaching that the whole human race has a share in the events of Christ's life, says that ''God has raised us up with him and enthroned us with him in heaven.'' ''(St. Cyril of Alexandria, On the Ascension of the Lord, Commentary of the Gospel of John, Book 9, John 14:2-3)
In other words, through Christ's Ascension, He brought us back in the presence of God the Father and restored our relationship as sons and daughters to God the Father. He has also seated us at the right hand of the Father in Him, the Son, restoring our authority and inheritance.
In the liturgy, the priest says Lift up your hearts. This is not a symbolic or metaphorical moment. It is an invitation to lift our hearts and to set our minds on the things above to recognize that, because of the Ascension, we are seated in the heavenly places, quite literally, for the Kingdom of God is within you.
Glory be to God forever. Amen.