Romans 8:3 says, "For that which the law could not do, in that it was weak through the flesh, God, sending His own Son in the likeness of the flesh of sin and concerning sin, condemned sin in the flesh." This verse shows that Christ died on the cross to condemn sin. We should not think that it is good enough just to be redeemed from sin. This sin also has to be put to death.
Sin is personified. It has some living element in it. Sin is the embodiment of Satan. The embodiment of God is Christ. Satan imitated God to have an embodiment, and Satan's embodiment is called sin in the Bible. Thus, in Romans 7 sin is a person. Sin, the embodiment of Satan, dwells in us, kills us, defeats us, and lords it over us. In Romans 8 Christ came in the likeness of the flesh of sin for the purpose of condemning sin. Sin is a robber. Surely God has to condemn this robbing one. Sin is a living person, the very person of the evil one.
Satan got into man's flesh. He was clever, but God is more clever than he is. God could have said, "Satan, you got into the body I created for man and took possession of it. You have been enjoying it as your dwelling place, but now it has become your trap." We may use a mousetrap as an illustration of this. The mouse might have thought he was clever to get the bait, but eventually he became trapped and could not run away. Our flesh was used by God as a trap for Satan. Satan was like a mouse running freely in this universe. One day, however, he became trapped in the flesh.
After he was trapped in the flesh, the Son of God became flesh. We may say that the Word became a man and that God was manifested in a man, but the Bible does not say it in this way. John 1:14 says that the Word became flesh, and 1 Timothy 3:16 says that God was manifested in the flesh. Satan took the flesh as his dwelling place, but the Lord came and brought this dwelling place, the flesh, to the cross. God condemned the personified sin by becoming flesh and carrying the flesh to the cross.
By His death on the cross, Christ destroyed the devil (Heb. 2:14). Satan stirred up the Jewish people and the Roman soldiers to put Jesus on the cross, but when he did this, he was helping to nail his dwelling place, the flesh, on the cross. He did not realize that by doing this, he was helping the Lord to put him to death. Satan was in the flesh, and Christ crucified this flesh on the cross to destroy the devil.
Although the Bible says that Christ became flesh, we need to realize that according to the Bible, He was only in the likeness of the flesh of sin (Rom. 8:3), and He did not have the sin of the flesh (2 Cor. 5:21; Heb. 4:15). John 3:14 tells us that Christ was lifted up on the cross as a serpent, not a serpent of poison but a serpent of brass. The brass serpent surely had the same form as the serpent of poison, but it did not have the poison. Christ was in the likeness of the serpent, the likeness of the flesh of sin. The Bible tells us that when He was crucified there, we were also crucified with Him (Gal. 2:20a). We also need to realize that even Satan was crucified on the cross with Him. When Christ was hanging on the cross, in the eyes of God, He was not only in the form of man but also in the form of a serpent. The serpent and man had become one, so to be in the form of man is to be in the form of the serpent.