This is a key moment in this story. The beginning of John 1 explained that the Lord is perfect, infinite love which gave itself expression as divine truth. The duality of love and expression formed a template for humanity, which meant that the Lord’s duality made him the ultimate, divine human. It showed that the divine truth was the power of creation, and that the Lord shared that truth with humanity from the outset, so that people could receive His love and return it. But people kept turning away, and the Lord had to keep expressing his love in more and more external forms to maintain a connection.

By mentioning John the Baptist, the chapter showed that the Jews of the time still had the truth – the Lord’s Word – contained inside the rough-hewn images of the Old Testament. But they were so steeped in evil loves and false thinking that the connection to the Word – to the love within the Old Testament – was about to be snipped forever.

So the Word became flesh. The Lord passed the full expression of His love and His full humanity into physical flesh as Jesus. That way He could once again show the life within the existing Scriptures and could make His own life and His own words part of an expanded expression of truth for a new age of humanity. People could no longer see and feel the Lord’s love through the Old Testament, but they could see and feel it in the face and hands and words of Jesus.

The "glory" here expresses the blinding brilliance of that truth. The "Father" represents the Lord’s actual love itself, and being "begotten" means that the love was expressed in the form of truth. Being full of "truth" has a pretty obvious meaning, but "grace" means an affection, a love for what is true.

The Lord had to come. He had to let His humanity flow down into the flesh, into the most external of forms, because that was the only way we were going to see and embrace it.

(References: A Brief Explanation of the Teachings of the New Church 117; The Apocalypse Explained 1069 [3]; The Word 20; True Christian Religion 3, 85)

870. Having an eternal gospel. That this signifies concerning His Advent, and concerning the salvation of those who believe in Him, is evident from the signification of gospel, as denoting the Advent of the Lord, and, in such case, the salvation of those who then believe in Him. That the Advent of the Lord has taken place, and also is about to take place, at the Consummation of the Age, that is, at the end of the old church and the beginning of the new; and that at the same time, also, the Last Judgment, may be seen above (n. 612); and from the signification of eternal, as denoting the Divine as to Manifestation (existere). There are two universals by which the Divine is expressed - "Infinite" and "Eternal." Infinite is the Divine as to its Being (esse); and eternal is the Divine as to its Manifestation (existere); and each is to be understood apart from space and time. He who thinks from space and time of the infinite and eternal falls into errors; for space and time are proper to nature, in which man's ideas are, while he lives in the natural world. But this is not the case when he leaves this world and comes into heaven. Spaces and times appear, indeed, in heaven, in a way quite similar to their appearance in the world; but they are only appearances of the states of the angels; for the states of their affection and thought therefrom takes on the appearances before their external senses of spaces and as times; yet they are not spaces and times such as pertain to the natural world. The nature of spaces and times in heaven will be evident from two articles in the work concerning Heaven and Hell, where this subject is treated of.

Because the Divine is infinite and eternal, therefore in all things in general and particular which come from the Divine, there is the Infinite and Eternal. This is why the gospel, by which is signified the Advent of the Lord and the salvation of the faithful, is called eternal. That "infinite and eternal" are said of the Lord alone may be seen above (n. 23, 286).

That the gospel signifies the Advent of the Lord, and the salvation of the faithful which then takes place, is clear from the passages in both Testaments where it is mentioned; these have been adduced above (n. 612). But as to the Advent of the Lord, it is believed by some that the Lord will come again in person, and, indeed, to carry out the Last Judgment, because it is said in Matthew:

The disciples drew near, saying unto Jesus, "Tell us what shall be the sign of thy coming, and of the consummation of the age" (24:3).

And after the Lord had foretold to them the states of the church, successively decreasing even to its devastation and consummation, He said,

"Then shall appear the sign of the Son of man; and they shall see the Son of man coming in the clouds of heaven, with power and great glory. Watch therefore, because ye know not the hour in which your Lord will come" (Matthew 24:30, 39, 42). Also in John (21:22).

His Advent does not there mean His Advent in person; but that He will then reveal Himself in the Word, that He is Jehovah, the Lord of heaven and earth; and that He alone is to be worshipped by all who shall belong to His New Church, which is meant by the New Jerusalem. To this end also He has now opened the internal or spiritual sense of the Word, in which sense the Lord is everywhere treated of. This is also what is meant by His coming in the clouds of heaven with glory;

See Matthew 24:30; 26:64; Mark 13:26; 14:62; Luke 21:27.

That the clouds of heaven signify the Word in the letter, and the glory its spiritual sense, may be seen above (n. 36, 594). Because He Himself is the Word, as He is called in John (1:1, 2, 14); therefore the revelation of Himself in the Word is His Advent.