In the Old Testament, the thought of God being man's life has six main points. First, God's creating of living things indicates that God is the God of life. Second, God's creating of man in His image indicates that God wants man to have God as his life so that man can express God. Third, God's putting man before the tree of life indicates that God desires that man would take Him, signified by the tree of life, as man's life. Fourth, Satan's tempting of man to take the tree of knowledge indicates that Satan wants to keep man from taking God as his life. Fifth, God's prohibiting of the fallen man, by the cherubim and the flaming sword, from taking the tree of life indicates that God's glory (signified by the cherubim), holiness (signified by the flame), and righteousness (signified by the sword) do not allow sinful man to abuse the life of God. Sixth, through the redemption of Christ, as typified by the propitiation accomplished with the sacrifices, the Old Testament saints had the right to partake of God as the fountain of life for their satisfaction and enjoyment. These six items are the main points in the Old Testament concerning the matter of the divine life in its relationship to us.
In the New Testament, the thought of God being man's life begins with the incarnation. God came to be incarnated that man may receive Him as grace and reality, both of which are God Himself to be man's life as man's eternal portion (John 1:14, 16, 4). God came to reach man. His journey, His coming, to reach man includes six steps, and the destination of His journey is man's spirit. First, He came as life that man may have the divine life and have it abundantly (John 14:6a; 11:25a; 10:10b; 1 John 5:11-12). Second, He laid down His own human life for man and took it again to release His divine life that He may dispense it into His believers (John 10:11, 15b, 17-18a, 28a). Christ's laying down of His life was His dying on the cross for our redemption. Christ's redemption made a way through all the obstacles, just as a tunnel provides a way through a mountain. In order to impart His divine life into our spirit, Christ died for our redemption.
In the third step of His coming, Christ was lifted up on the cross in the form of the serpent that His believers may have God's eternal life—the uncreated, indestructible life (John 3:14-15; Heb. 7:16). In this aspect of His death, Christ died not only in the form of a man, but also in the form of a serpent (John 3:14; Num. 21:8-9). In the eyes of God, all fallen men are serpents (Matt. 12:34), because they all have the serpentine nature within them. Outwardly, we may appear to be ladies and gentlemen, but inwardly we are serpentine. Because we are serpents, Christ died on the cross in the form of the serpent. Because as fallen men we have the poison of sin within us, we are real serpents. But Christ, like the brass serpent, had only the form of the serpent, because He did not have the poison of sin within Him (Rom. 8:3; 2 Cor. 5:21; Heb. 4:15). Christ's coming in the form of the serpent was to deal with our serpentine nature in order to impart Himself as life to us. So, His dying on the cross in the form of a serpent was a further step in God's coming to be our life.