Rightly, therefore, the Lord again promises milk to the righteous, that the Word may be clearly shown to be both, "the Alpha and Omega, beginning and end; "
In the same way the Lord applied to himself two Greek letters, the first and the last, as figures of the beginning and the end which are united in himself. For just as Alpha continues on until it reaches Omega and Omega completes the cycle back again to Alpha, so he meant to show us that in him is found the course of all things from the beginning to the end and from the end back to the beginning. Every divine dispensation should end in him through whom it first began, that is, in the Word made flesh. Accordingly, it should also end in the same way in which it first began. So truly in Christ are all things recalled to their beginning. So the faith has turned away from circumcision back to the integrity of the flesh, as it was in the beginning. So, too, there is liberty now to eat any kind of food, with abstention from blood alone, as it was in the beginning. There is a unity of marriage, as it was in the beginning. There is a prohibition of divorce, which was not in the beginning. Finally, the whole man is called once more to paradise, where he was in the beginning.
Meanwhile, let this be my immediate answer to the argument which they adduce from the Revelation of John: "I am the Lord which is, and which was, and which is to come, the Almighty; " and from all other passages which in their opinion make the designation of Almighty God unsuitable to the Son.
The Godhead of the Son is the Father’s. It is indivisible. Thus there is one God and none other but he. So, since they are one, and the Godhead itself one, the same things are said of the Son, which are said of the Father, except his being said to be Father. For instance, it is said that he is God: “And the Word was God.” It is said that he is Almighty, “Thus says he who was and is and is to come, the Almighty.” It is said that he is Lord, “one Lord Jesus Christ.” It is said that he is Light, “I am the Light,” that he wipes out sins, “that you may know,” he says, “that the Son of man has power upon earth to forgive sins,” and so with other attributes. For “all things,” says the Son himself, “whatsoever the Father has, are mine”; and again, “And mine are yours.”
The martyrdom of the blessed apostles has consecrated this day for us. It was by despising the world that they earned this renown throughout the whole world. Peter was the first of the apostles and Paul the last of the apostles. The first and the last were brought to one and the same day for martyrdom by the First and the Last, by Christ. In order to grasp what I’ve said, turn your minds to the Alpha and the Omega. The Lord himself said plainly in the Apocalypse, “I am the Alpha and the Omega, the first”—before whom is nobody—“the last”—after whom is nobody; he precedes all things and sets a term to all things. Do you want to gaze upon him as the first? “All things were made through him.” Do you seek him as the last? “For Christ is the end of the law, that every one who has faith may be justified.” In order for you to live at some time or other, you had him as your creator. In order for you to live always, you have him as your redeemer.
Alpha means beginning, and Omega means the end. Therefore he says, “I am the first and the last (Rev. 1:17).” He professes by the first that God has no beginning, and by the last that He has no end. But with there is nothing that is without beginning and end, he says this for us instead of saying, “without beginning nor end.” This is what God also said through Isaiah, “I, God, am first, and for the things coming, I Am.(Is. 41:4)”
The Almighty, and Lord of creation: He calls God Lord over the spiritual and visible creation.
[AD 215] Clement of Alexandria on Revelation 1:8