4 John to the seven churches which are in Asia: Grace be unto you, and peace, from him which is, and which was, and which is to come; and from the seven Spirits which are before his throne;
[AD 304] Victorinus of Pettau on Revelation 1:4
"Grace unto you, and peace, from Him which is, and which was, and which is to come." He is, because He endures continually; He was, because with the Father He made all things, and has at this time taken a beginning from the Virgin; He is to come, because assuredly He will come to judgment.

"And from the seven spirits which are before His throne." We read of a sevenfold spirit in Isaiah,1 -namely, the spirit of wisdom and of understanding, the spirit of counsel and might, of knowledge and of piety, and the spirit of the fear of the Lord.

[AD 430] Augustine of Hippo on Revelation 1:4
The number seven signifies the perfection of the universal Church, for which reason the Apostle John writes to the seven churches, showing in that way that he writes to the totality of the one Church. City of God 17.4
[AD 542] Caesarius of Arles on Revelation 1:4
Asia means “elevated,” by which the human race is indicated. These seven churches and the lampstands are to be seriously considered because it is the sevenfold grace which is given by God through Jesus Christ, our Lord, to us of the human race who have believed. For he himself promised to send to us the Spirit Paraclete from heaven, whom he also sent to the apostles who were seen to be in Asia, that is, in the prideful world, where he also gave the sevenfold grace to the seven churches, that is to us, through his servant John.

[AD 585] Cassiodorus on Revelation 1:4
him that is. He wanted His eternity to be denoted by the present tense. This use of present time “today” is acknowledged to be peculiar to the divine Scriptures in this sense of perpetuity.
[AD 600] Apringius of Beja on Revelation 1:4
What is the importance of the people of Asia that they alone deserve to receive the apostolic revelation? However, there is a mystery in the number and a sacrament in the name of the province. First, let us discuss the meaning of the number, because both the number six and the number seven are always used in the law with a mystical meaning: “For God made heaven and earth in six days,” and “on the seventh day he rested from his works” and “on it,” it says, “they shall enter again into my rest.” The number seven, therefore, signifies the period of the present life, so that the apostle is not merely writing to seven churches and to that world in which he was then present, but it is understood that he is giving these writings to all future ages, even to the consummation of the world. Therefore, he mentions the number in a most holy manner, and he names “Asia,” which means “elevated” or “walking,” indicating that celestial fatherland which we call the “catholic church.” For exalted by the Lord and always moving toward the things which are above, it is the church which advances by spiritual exercises and is always desirous of the things of heaven.

[AD 600] Apringius of Beja on Revelation 1:4
Here is that mystery of the number seven which is everywhere indicated. Here the seven spirits are introduced, which are one and the same Spirit, that is, the Holy Spirit, who is one in name, sevenfold in power, invisible and incorporeal, and whose form is impossible to comprehend. The great Isaiah revealed the number of its sevenfold powers when he wrote: “the Spirit of wisdom and understanding”—that through understanding and wisdom he might teach that he is the creator of all things—“the Spirit of counsel and might”—who conceived these things that he might create them—“the Spirit of knowledge and piety”—who governs the creation with piety by the exercise of his knowledge and whose purposes are always according to mercy—“the Spirit of the fear of the Lord”—by whose gift the fear of the Lord is manifested to rational creatures. This is itself the sacred character of the Spirit who is to be worshiped. It includes rather the ineffable praise, and does not indicate any form of nature.

[AD 614] Andreas of Caesarea on Revelation 1:4
Although there are many churches in every place, he wrote to seven only. For through the number seven he indicates the mystery of the church which exists everywhere and that which corresponds to the present life in which there is a sevenfold period of days. And therefore he makes mention of seven angels and seven churches to which he says, “Grace to you and peace from the tri-hypostatic deity.” Through the phrase “who is” the Father is indicated, who spoke to Moses: “I am Who I am.” Through the phrase “who was” the Word is indicated, who was in the beginning with God. And through the phrase “who is to come” the Paraclete is indicated, who always visits the children of the church in holy baptism but will come more perfectly and more clearly in the age to come. It is possible to recognize in the seven spirits the seven angels who have received the governance of the churches. These are not numbered with the most divine and royal Trinity but are mentioned together with it as servants, even as the divine apostle says: “I testify to you before God and the elect angels.” These phrases may be understood also in another manner. The phrase “who is and who was and who is to come” may signify the Father, who encompasses in himself the beginning, the middle and the end of all things.

[AD 735] Bede on Revelation 1:4
John to the seven, etc. Through these seven churches, he writes to the whole Church. For the universality is often designated by the number seven, as this whole age is revolved in seven days.

[AD 735] Bede on Revelation 1:4
Grace to you, etc. He wishes us grace and peace from the eternal God the Father, and from the sevenfold Spirit, and from Jesus Christ, who in the assumed man bore witness to the Father. He names the Son third, of whom he was going to speak more. He names him last as well, because he is the first and the last, since he had already named him in the Father by saying, who is to come.

[AD 990] Oecumenius on Revelation 1:4
This is just like saying, “Grace to you from the God of all of us.” For the Father calls Himself “Being/ONTA” when he talked to the most wise Moses at the bush, saying, “I am The One Who Is,(Ex. 3:14)” and this evangelist said “He was” concerning the Son, saying, “In the beginning was the Word, and the Word was with God, and the Word was God,(Jn. 1:1)” and again in the first of the Catholic Epistles, “That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon, and our hands have handled, of the word of life.(1Jn. 1:1)”

And by that is to come he means the Holy Spirit. For the Spirit was not only there on the day of Pentecost, according to the account in Acts, but He is always present, too, to the souls who are worthy to receive Him...

The seven spirits are seven angels; but not as being equally honored or coeternal were they included with the Holy Trinity — far from it — but as genuine servants and faithful slaves. For the prophet says to God, “For all things are your slaves.” In all things the angels are also comprised. And again the same prophet says about them, “Bless the Lord, all his hosts, his ministers that do his will.” In this fashion, too, the apostle addressed Timothy when writing the first letter: “I charge you,” he says, “before God and Jesus Christ and the elect angels.” Further, by saying who are before his throne John gave added testimony to their rank as servants and ministers, and certainly not as having equal dignity.

[AD 1198] Nerses of Lambron on Revelation 1:4
before his throne. Now the seven spirits indicate the activity of the life-giving Spirit which directed Christ, God who was made man for us.
[AD 1349] Nicholas of Lyra on Revelation 1:4
This “7” is understood as the Church established in the world. St. Gregory says in Homily 25, “Because in 7 days all time is comprehended; the number 7 is a proper figure for the whole. Grace unto you In the present life. And peace in the future, for there the humanity will be completely tamed. From Him who is That is, from the eternal God. According to Boethius in the Consolation of Philosophy, “Eternity is endless life possessed all at once in its totality and its perfection. Nevertheless, his simplicity is not apprehended by us except by a comparison to time; for we understand in terms of succession and time. For he assists at every time, even infinitely as it were; therefore, this is expressed to us through the distinctions of present, past, and future time. And from the 7 spirits That is, from all the angels who are ministers of our salvation. Who are before His throne, Prepared to follow His will.