Rev 4:1

“"After this, I beheld, and, lo, a door was opened in heaven." The new testament is announced as an open door in heaven. "And the first voice which I heard was, as it were, of a trumpet talking with me, saying, Come up hither." Since the door is shown to be opened, it is manifest that previously it had been closed to men. And it was sufficiently and fully laid open when Christ ascended with His body to the Father into heaven. Moreover, the first voice which he had heard when he says that it spoke with him, without contradiction condemns those who say that one spoke in the prophets, another in the Gospel; since it is rather He Himself who comes, that is the same who spoke in the prophets. For John was of the circumcision, and all that people which had heard the announcement of the Old Testament was edified with his word. "That very same voice," said he, "that I had heard, that said unto me, Come up hither." That is the Spirit, whom a little before he confesses that he had seen walking as the Son of man in the midst of the golden candlesticks. And he now gathers from Him what had been foretold in similitudes by the law, and associates with this scripture all the former prophets, and opens up the Scriptures. And because our Lord invited in His own name all believers into heaven, He forthwith poured out the Holy Spirit, who should bring them to heaven.”

“"Afterwards," John said, "I saw." After seeing the vision, he remembered that he had seen another. The interval in time belongs not to the events but to the visions. If one were to describe a single event in different ways, it would be the descriptions that differ in time, not what took place at one time. In this way, he retraces the whole span of the church using various figures to describe it. "Behold," he says, "an open door in heaven." The open door represents Christ, who was born, suffered and was raised. Christ is the gateway, as he himself said, "I am the door." Heaven represents the church because it is the habitation of God where the celestial realities are effected. This is why we pray that the will of God be done on earth even as it is in heaven. Sometimes, however, the church is represented by both heaven and earth, since the earth comes into agreement with heaven, either when the unfaithful are won by the righteous proclamation of the faithful, or when the flesh is subdued by the Spirit, or when the things of the earth are reconciled and united to the things of heaven.”

“This is, therefore, the voice of prophecy of which it is said, "Lift up your voice like a trumpet." One has gone up and ascended who, having despised the world, is either compelled to come to the church or obtains admission to her. He ascends from the valley of tears to the height of that dignity of which we read, "Come, let us go up to the mountain of the Lord and to the house of the God of Jacob, and he will teach us his ways." However, the faithful are also invited to ascend to heaven when they are commanded to seek and to taste what is in heaven and not what is upon the earth. For when a neophyte in the church is taught that Christ suffered, was raised and has ascended to the Father, and then beyond these things is taught and instructed spiritually to contemplate him in the Father according to the form of God, he is rightly said to ascend, since he will see the secrets of the mysteries in which he has believed. Therefore, the Lord said, "Do not touch me, for I have not yet ascended to the Father," wishing this touching to be understood as belief.”

“After this, I looked, and behold, a door open in heaven. After describing the works of the Church, what it was and what it would be like, he recapitulates from the birth of Christ, intending to say the same things differently. For he repeats the entire time of the Church in various figures in this book. Behold, he says, a door open in heaven. Fittingly, he sees a heavenly door about to ascend, to whom high mysteries are promised to be revealed. Or because Christ is the door, he who believes in Him born and suffered ascends to heaven, that is, to the height of the Church, and sees future spiritual events as he says.”

“After these things I looked, and behold a door was opened in heaven. The Redeemer's Nativity is recapitulated, and these things had already been said with various other symbols; as when one relates one event in different ways, the narrations will each have a different time, but not the event itself, which happened in one time. We should however ask the question of why John does not disclose the time of his prophecy, while other prophets used to disclose by the kings the length of the interval between one vision and another. It is because he is informing us that the whole time of the Church should be related to that continuous day of resurrection about which it is said, Blessed is he that hath part in the first resurrection; [Rev. 20:6] for the first resurrection, that is the one by which souls rise again from the death of sin to the life of justice, is now going on all the time. Now with what eyes did John see this door? As far as the figurative vision is concerned, he did not of course see it with the eyes of the flesh, but with those of the mind; but for what concerns the truth of the thing itself, truth which had already been manifested when the Lord had appeared in the flesh, not only did he see it with the eyes of the flesh, but he even touched it with his hands. The open door represents Christ, who has already been manifested to all the faithful by being born, dying, and rising again. It is appropriate for this door to be seen in heaven, that is in the Church, because it is in the Church that people proclaim and believe that our Redeemer was born, suffered, was resurrected, and went up to heaven. And the first voice which I heard, was, as it were, of a trumpet speaking with me, saying: Come up hither. Whither, but to the door and heaven, that is Christ and the Church? And with what steps, but those of faith? It is right for John to be invited to this by the first voice, because every one of the elect, in order that they may reach the mysteries of the true faith through the Gospel without the foot of belief striking against any obstacle, is strengthened by the teaching of the Old Testament, which preceded the new teaching. It is also right for this voice to be compared to a trumpet, because it is calling us to a spiritual war; whence this: Lift up thy voice like a trumpet. [Is. 58:1] In what is said after that, I will shew thee the things which must be done hereafter, he does not deny that the Church already has high honors, but he shows that they will last until the end of the world.”

“It is not that there is literally a door in heaven that opens and closes at times, but it was shown to the evangelist in this way so that he might see the things above the heavens. For with every door opened, what lies within must inevitably be seen. And I heard a voice, which sounded like a trumpet, saying these words to me: Come up here so that you may see what is to come.”