14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.

[And the Word was made flesh] That very person who was in the beginning - who was with God - and who was God, (verse 1), in the fullness of time became flesh - became incarnated by the power of the Holy Ghost, in the womb of the virgin. Allowing this apostle to have written by Divine inspiration an absolute and incontestable proof of the proper and eternal Godhead of Christ Jesus?

[And dwelt among us] And tabernacled among us; the human nature which he took of the virgin, being as the shrine, house or temple in which his immaculate Deity condescended to dwell. The word is probably an allusion to the Divine Shechinah in the Jewish temple; and as God has represented the whole Gospel dispensation by the types and ceremonies of the old covenant, so the Shechinah in the Jewish temple pointed out this manifestation of God in the flesh. The word is thus used by the Jewish writers: it signifies with them a manifestation of the Devine Shechinah.
The original word, [a greek word, transliterated skano], from [another greek word, transliterated skia], a shadow, signifies: 1. To build a booth, tent or temporary hut for present shelter or convenience, and does not properly signify a lasting habitation or dwelling place; and is therefore fitly applied to the human nature of Christ, which, like the tabernacle of old, was to be here only for a temporary residence for the eternal Divinity. 2. It signifies to erect such a building as was used on festival occasions, when a man invited and enjoyed the company of his friends. To this meaning of the word, which is a common one in the best Greek writers, the evangelist might allude, to point out Christ's associating his disciples with himself; living, conversing, eating and drinking with them; so that, while they had the fullest proof of his Divinity by the miracles which he wrought, they had the clearest evidence of his humanity by his tabernacling among, eating, drinking and conversing with them.

[We beheld his glory] This refers to the transfiguration, at which John was present, in company with Peter and James (Matthew 17:1-5.)

[The glory as of the only begotten] That is, such a glory as became, or was proper to, the Son of God. There is also an allusion to the manifestation of God above the ark in the tabernacle (see Exodus 25:22 and Numbers 7:89 ); and this connects us with the first clause, He tabernacled, or fixed his tent among us. While God dwelt in the tabernacle, among the Jews, the priests saw his glory. While Jesus dwelt among men his glory was manifested in his gracious words and miraculous acts.

[The only begotten of the Father] That is, the only person born of a woman, whose human nature never came by the ordinary way of generation; it being a unique creation in the womb of the virgin by the energy of the Holy Ghost.

[Full of grace and truth] Full of favor, kindness, and mercy to men; teaching the way to the kingdom of God with all simplicity, plainness, dignity and energy of truth.

15 John bare witness of him, and cried, saying, This was he of whom I spake, He that cometh after me is preferred before me: for he was before me.

[Of him] The glorious personage before mentioned; John the Baptist, whose history was well known to the persons to whom this Gospel came in the beginning, bare witness; and he cried, - being deeply convinced of the importance and truth of the subject he delivered his testimony with the utmost zeal and earnestness - saying, this is he of whom I spake, He that cometh after me - for I am no other than the voice of the crier in the wilderness (Isaiah 40:3,) the forerunner of the Messiah.

[Was before me] Speaking by the prophets and warning your fathers to repent and return to God, as I now warn you: for he was before me - he was from eternity, and from him I have derived both my being and my ministry.

16 And of his fulness have all we received, and grace for grace.

[And of his fullness] (Continuing the thought of verse 14) Of the plentitude of his grace and mercy, by which he made an atonement for sin, and of the plentitude of his wisdom and truth, by which the mysteries of of heaven have been revealed.

17 For the law was given by Moses, but grace and truth came by Jesus Christ.

[The law was given by Moses] The law of Moses, however excellent in itself, was incapable of expiating sin by its sacrifices, but was intended to convict men of sin and prepare them for the Gospel. See Hebrews 10:1-4, Romans 3:19:20, Galatians 3:24.

[But grace and truth] Came to all mankind through Jesus Christ, who is the mediator of the new covenant, as Moses was of the old; (Matthew 5:17-18, Hebrews 10:8-18, Romans 5:1-11).

18 No man hath seen God at any time, the only begotten Son, which is in the bosom of the Father, he hath declared him.

[No man hath seen God at any time] Moses and others heard his voice and saw the cloud and the fire which were symbols of his presence, but such a manifestation of God, as had now taken place in the person of Jesus Christ, had never before been exhibited in the world. It is likely that John uses the word seen for known, as in chapter 3:32, 1 John 3:2, and 3 John 1:11; and this sense the latter clause of the verse seems to require; - no man, no matter how highly favored, has fully known God at any time, in any nation or age; the only begotten Son, who is in the bosom of the Father, who is intimately acquainted with the Most High, he has declared him unto men; for in this sense the word is used by the best Greek writers.
Lying in the bosom is spoken of in reference to the Asiatic custom of reclining while at meals; the person who was next to the other was said to lie in his bosom; and he who had this place in reference to the master of the feast was supposed to share his particular regard and to be in a state of utmost favor and intimacy with him.