Rom. 8:3 indicates that although this flesh was the flesh of sin, it had only the likeness of the flesh of sin and did not have the sin of the flesh. It is the Word who became such flesh, and this Word was God, the complete Triune God (v. 1). That the Word became flesh means that the Triune God became a man of flesh in the likeness of a sinful man. By so doing God entered into sinful man and became one with sinful man. However, He had only the likeness of a sinful man and not the sin of a sinful man. Hence, He was a sinless God-man, the complete God and the perfect man, having two natures, the divine nature and the human nature. Although His two natures were mingled to produce a God-man, the individual characteristics of the two natures remained distinct; the two natures did not intermix to form a third nature. Rather, the divine nature existed in the human nature and was expressed through the human nature, full of grace, which is God enjoyed by man, and reality, which is God obtained by man. In this way the invisible God was expressed so that men can obtain and enjoy Him as their life for the fulfillment of His New Testament economy.
God's becoming flesh was contrary to the teaching of the Gnostics of that time. The Gnostics maintained that since the flesh is an evil substance, God, who is pure, could never be united with the evil flesh. Using the teaching of the Gnostics as a basis, the Docetists denied that Christ had come in the flesh (1 John 4:2). John wrote this Gospel in part to refute the heresy of the Docetists and to prove strongly that Christ, the God-man, is indeed God who became flesh (having only the likeness of the flesh of sin but not the sin of the flesh) that through this flesh, on the one hand, He might destroy the devil (Heb. 2:14) and put away the sins of man (Heb. 9:26), and, on the other hand, God might be united with man and be expressed through humanity for the fulfillment of His glorious purpose, a purpose He planned in eternity past for eternity future.
The deep thought of the Gospel of John is that Christ, the incarnate God, came as the embodiment of God, as illustrated by the tabernacle (v. 14) and the temple (John 2:21), so that man could contact Him and enter into Him to enjoy the riches contained in God. Both the tabernacle and the temple had an outer court, a Holy Place, and a Holy of Holies. Therefore, John points out first that Christ was the Lamb (who took away sin — v. 29) offered on the altar, which signifies the cross, in the outer court of the tabernacle, and then that He was like the bronze serpent (which caused man to have life) lifted up on the pole (John 3:14), which signifies the cross. This shows how Christ in His redemption was received by His believers that they might be delivered from sin and obtain life and might enter into Him as the embodiment of God, typified by the tabernacle, to enjoy all the riches that are in God. The foot-washing in ch. 13 may be considered the washing in the laver in the outer court of the tabernacle, which washed away the earthly defilement of those who drew near to God, so that their fellowship with God and with one another could be maintained. In ch. 14 those who receive Christ are brought by Him into the Holy Place to experience Him as the bread of life (John 6:35), signified by the showbread, and as the light of life (John 8:12; 9:5), signified by the lampstand. Eventually, in ch. 17, through the highest and most mysterious prayer, which is typified by the burning incense on the golden incense altar, those who enjoy Christ as life and as light are brought by Him into the Holy of Holies to enter with Him into the deepest enjoyment of God and to enjoy the glory that God has given Him (John 17:22-24).