“How was the incarnate Son ‘made perfect’? Certainly, nothing was lacking in His divine nature. And His humanity was always without sin. In what sense, then, did He need to be made perfect?
A hint is provided when Hebrews 2:10 says that God made Christ ‘perfect through suffering.’ This idea is expanded when Hebrews 5:8 says that Jesus ‘learned obedience through what He suffered.’ The Son was made perfect when, over the course of His earthly life, He learned to obey the Father, especially by enduring suffering.
An illustration will help. Imagine that in the first-century Jerusalem Gazette a listing appears in its ‘Help Wanted’ section for the job of Redeemer of the world. There are three requirements for the job.
First, the applicant must be God; no others need apply. That would narrow the job pool to three. Second, the applicant must also have become man. That would exclude all but one. The point of the passages in Hebrews that teach that the incarnate Son was made perfect is found in the third qualification in the job description for Redeemer.
Not only must the applicant be God incarnate; he must also have on-the-job experience. Although Jesus’s humanity was never sinful, in God’s plan it must be tried and found true. God did not send His Son to earth as a thirty-three-year-old to die and be raised. He sent Him as an infant in order for Him to experience human life, with all of its trials and temptations, triumphantly.
It is critical to note the purpose for the Son’s being made perfect, that is, experientially qualified to be Savior by learning obedience through suffering. ’And being made perfect, He became the source of eternal salvation to all who obey Him, being designated by God a high priest after the order of Melchizedek’ (Heb. 5:9–10).
Jesus’s sinless life was necessary for Him to become the source of eternal salvation for every believer. His proven sinlessness enabled Him to die and rise to save sinners. It qualified Him to offer Himself as a sacrifice in His ministry as our great ‘high priest after the order of Melchizedek.’”
–Robert A. Peterson, Salvation Accomplished by the Son: The Work of Christ (Wheaton: Crossway, 2012), 49.