“So then the Lord Jesus, after he had spoken to them, was taken up into heaven, and sat down at the right hand of God.” Christ’s body was glorified at the moment of his Resurrection, as proved by the new and supernatural properties it subsequently and permanently enjoys. But during the forty days when he eats and drinks familiarly with his disciples and teaches them about the kingdom, his glory remains veiled under the appearance of ordinary humanity. Jesus’ final apparition ends with the irreversible entry of his humanity into divine glory, symbolized by the cloud and by heaven, where he is seated from that time forward at God’s right hand. Only in a wholly exceptional and unique way would Jesus show himself to Paul “as to one untimely born”, in a last apparition that established him as an apostle.
The veiled character of the glory of the Risen One during this time is intimated in his mysterious words to Mary Magdalene: “I have not yet ascended to the Father; but go to my brethren and say to them, I am ascending to my Father and your Father, to my God and your God.” This indicates a difference in manifestation between the glory of the risen Christ and that of the Christ exalted to the Father’s right hand, a transition marked by the historical and transcendent event of the Ascension.
This final stage stays closely linked to the first, that is, to his descent from heaven in the Incarnation. Only the one who “came from the Father” can return to the Father: Christ Jesus. “No one has ascended into heaven but he who descended from heaven, the Son of man.” Left to its own natural powers humanity does not have access to the “Father’s house”, to God’s life and happiness. Only Christ can open to man such access that we, his members, might have confidence that we too shall go where he, our Head and our Source, has preceded us.
“and I, when I am lifted up from the earth, will draw all men to myself.” The lifting up of Jesus on the cross signifies and announces his lifting up by his Ascension into heaven, and indeed begins it. Jesus Christ, the one priest of the new and eternal Covenant, “entered, not into a sanctuary made by human hands. . . but into heaven itself, now to appear in the presence of God on our behalf.” There Christ permanently exercises his priesthood, for he “always lives to make intercession” for “those who draw near to God through him”. As “high priest of the good things to come” he is the centre and the principal actor of the liturgy that honours the Father in heaven.
Henceforth Christ is seated at the right hand of the Father: “By ‘the Father’s right hand’ we understand the glory and honour of divinity, where he who exists as Son of God before all ages, indeed as God, of one being with the Father, is seated bodily after he became incarnate and his flesh was glorified.”
Being seated at the Father’s right hand signifies the inauguration of the Messiah’s kingdom, the fulfilment of the prophet Daniel’s vision concerning the Son of man: “To him was given dominion and glory and kingdom, that all peoples, nations, and languages should serve him; his dominion is an everlasting dominion, which shall not pass away, and his kingdom one that shall not be destroyed.” After this event the apostles became witnesses of the “kingdom [that] will have no end”.
From the Catechism of the Catholic Church 659-664