The Lord when in the world fulfilled everything in the Word, and thus became the Word, that is, Divine truth, even in its outermost form.
The Lord's fulfilling when in the world everything in the Word, and thus becoming Divine truth, that is, the Word, even in its outermost form, is what is meant by these words in John:
And the Word was made flesh, and dwelt among us, and we saw His glory, the glory as of the only-begotten of the Father, full of grace and truth. John 1:14.
Being made flesh is becoming the Word in its outermost form. The Lord showed the disciples, when He was transfigured, what the Word is like in its outermost form (Matt. 17:2ff; Mark 9:2ff; Luke 9:28ff). In these places it is said that Moses and Elijah were seen in glory; Moses means the Word which was written by means of him, and the historical part of the Word in general, Elijah the prophetical part. The Lord as seen by John in Revelation (1:13-16) was also represented as the Word in its outermost form. All the details of His description there mean the outermost form of Divine truth, that is, the Word. The Lord had indeed previously been the Word or Divine truth, but in its first beginnings; for it is said:
In the beginning was the Word, and the Word was with God, and the Word was God. John 1:1, 2.
But when the Word was made flesh, then the Lord became the Word even in its outermost form. That is why He is called 'the First and the Last' (Rev. 1:8, 11, 17; 2:8; 21:6; 22:12, 13; Isa. 44:6).