Who is the Sanctifier? The Sanctifier is the Son of God. In His original state and before His incarnation, the Son of God could not sanctify us. The Sanctifier today is not only the Son of God, but the Son of God incarnated. If He had never been incarnated, He would be unable to sanctify us. I say this strongly. Although He might have been able to sanctify you according to your concept of sanctification, He would have been unable to sanctify you according to God’s economy.
As the incarnated One, Christ is the Son of Man. This Son of Man could not sanctify us until He had been crucified, resurrected, glorified, and exalted. These are His qualifications for Him to be our Sanctifier. The incarnated Son of God needed to pass through death and resurrection that His humanity might be born of God and that He might be glorified and exalted into the position of His being Sanctifier.
In order to be the Sanctifier, Christ had to be produced as the Firstborn Son of God (1:6). Before Jesus Christ was resurrected, God did not have a Firstborn Son. He just had the only begotten Son. What is the difference between the Firstborn Son and the only begotten Son? As the only begotten Son, Christ did not have human nature. He only had the divine nature. When He was incarnated, He put on human nature. The thirty-three and a half years of His life on earth were a transitory state. On the one hand, He was still the only begotten Son of God; on the other hand, He had put on human nature. The divine nature within Him was the Son of God but the human nature was not. Therefore, during those thirty-three and a half years, Jesus was quite peculiar. He had the divine nature—that was the Son of God—but He also had on the human nature, and that was not the Son of God. That human nature had not been born of God. According to His divinity, His divine nature, He was the Son of God. But, before His resurrection, He had something that was not born of God—the human nature. He needed to pass through death and resurrection in order for that human part to be born of God. Psalm 2:7 is a strong basis for this: “Thou art my Son; this day have I begotten thee.” What was prophesied in Psalm 2:7 was fulfilled on the day of resurrection. This is proved by Acts 13:33 which, referring to the resurrection of Christ, quotes this verse from Psalm 2. In His human nature Christ was begotten as the Son of God on the day of resurrection. After this, He became the Firstborn Son of God. Now, as the Firstborn Son, He has both the divine nature and the human nature. As the only begotten Son of God, He did not have the human nature. While He was on earth after His incarnation, He had the human nature, but in those thirty-three and a half years His human nature had not been born of God. It was through His resurrection that the human part of His being was born of God. By this begetting, He became the Firstborn Son of God. While the only begotten Son of God had just the divine nature and not the human nature, Jesus today as the Firstborn Son of God has both natures. This is not a small thing; it is a great matter.
Let me ask you, are you sons of God? If you say yes, then what kind of sons of God are you? Are you like the Firstborn or like the only begotten? We are like the Firstborn Son of God because we are sons of God with a divine nature as well as a human nature. We are the sons of God according to the Firstborn Son, not according to the only begotten Son.
Now we can understand why the only begotten Son of God could not sanctify us and why the Firstborn Son of God can sanctify us. The Firstborn can sanctify us because He, like us, has two natures and because we have the same natures as He does. Our Sanctifier is not the only begotten Son of God; He is the Firstborn Son of God, the One who has the human nature as well as the divine nature. Because He and we are of the same two natures, He can sanctify us. Only when the Firstborn Son was produced could the Sanctifier come into His office to do His sanctifying work. This means that He had to pass through the process of incarnation, crucifixion, resurrection, glorification, and exaltation. After passing through this process, He became the Firstborn Son of God. In other words, the Firstborn Son of God was produced. This is our Sanctifier. He is qualified to be our Sanctifier, and we are qualified to be the sanctified.
He who sanctifies is Christ as the Firstborn Son of God, and those who are being sanctified are the believers of Christ as the many sons of God. Both the Firstborn Son and the many sons of God are born of the same Father God in resurrection (Acts 13:33; 1 Pet. 1:3). Both the Firstborn Son and the many sons are the same in the divine life and nature. Hence, He is not ashamed to call them brothers.