There are not only one God, one incarnation, and one crucifixion; there is also one resurrection.
If there were no resurrection, there would be no new creation. In the crucifixion all the things of the old creation were terminated, including Satan, the world, sin, and all the negative things. Now in resurrection the new creation has been germinated.
In the one resurrection Christ was begotten in His humanity to be the firstborn Son of God (Acts 13:33; Rom. 8:29). Christ as the firstborn Son of God was the first item germinated in the one resurrection. In His incarnation Christ put humanity upon Himself. This humanity was not divine. Romans 8:3 indicates that when Christ came in incarnation, He came "in the likeness of the flesh of sin." At the time of His crucifixion He brought His human part, which was in the likeness of the flesh of sin, to the cross and terminated it. But that was not all. In resurrection He germinated His humanity, making His humanity divine. In this way He was born as the firstborn Son of God. Christ Himself as the firstborn Son of God was the first item that needed to be germinated in His resurrection.
In the one resurrection Christ (the last Adam) was made the life-giving Spirit (1 Cor. 15:45b). In the one incarnation Christ as God was made a man (John 1:1, 14). As a God-man He lived in His humanity for thirty-three and a half years. Then He went to the cross and died there for the accomplishment of God’s eternal redemption. After a three day burial He rose up from the dead. In His one resurrection as the last Adam, a man in the flesh, He became the life-giving Spirit for the imparting of His divine life into His believers. This is marvelous and unique in the universe and in human history.
Before His resurrection Christ was the only begotten Son of God (John 3:16), but in resurrection He was born the firstborn Son of God (Acts 13:33; Rom. 8:29). This is something new. The word firstborn indicates that many sons will follow. The many sons were the second item Christ germinated in His resurrection. Through Christ’s one resurrection all God’s chosen people were regenerated to be the many sons of God (1 Pet. 1:3; Heb. 2:10-11). The one resurrection first germinated Jesus, who was in the likeness of the flesh of sin, to be born of God as the firstborn Son of God. This one resurrection also made Christ (the last Adam) the life-giving Spirit. Accompanying the previous two things, millions of God’s chosen people were regenerated to be the many sons of God in the one resurrection of Christ.
As the last Adam, Jesus was still in the old creation. Because the blood and flesh that Jesus put on in His incarnation were of the old creation, He put them on the cross. Through resurrection He became the life-giving Spirit and the firstborn Son of God. At the same time we as God’s chosen people were regenerated to be the many sons of God. Now the firstborn Son of God, the life-giving Spirit, and the many sons of God are all in the new creation through the one resurrection of Christ. This is the real base of the one Body, because these regenerated sons of God are the members who compose the Body of Christ. In His incarnation Christ became the first grain of wheat. Then through His death and resurrection He produced us as the many grains (John 12:24). These many grains in His one resurrection have become the members of His one Body.
(One Body and One Spirit, Chapter 1, by Witness Lee)