54. Thus we are shown that He who is to sanctify others was free from every stain, and from His mother’s womb He was consecrated to God in purity from the very beginning, in order that He may not be subject to the universal corruption of the human race.
So I understand it.
Our Lord came to the earth on a mission from the Father. He came “to save his people from her sins” (Matt. 1:21). Such a mission requires sinless perfection, however, for only an unblemished sacrifice could atone for sin. This was God’s purpose from the beginning.

When Adam sinned, God provided skins for him and his wife to cover their bodies and, by implication, to cover their sins (Gen. 3:21). Some time later, God revealed an elaborate process for both the selection and the steps for sacrificing animals to atone for sin. Of primary importance was the animal’s spotlessness and health. It must not have any defects, because the Lord is holy.

The author of Hebrews notes that this process was temporary. No animals could ultimately atone for all sins. Sin must be covered by an actual person. But who could possibly meet God’s demands? We think sinfully. We feel sinfully. We talk sinfully. We relate sinfully. We do sin, and we do it sinfully. If God seeks spotlessness, who could atone for sin (cf. Ps. 130)? There had to be someone uniquely separated by God for this task. That person is Jesus.

Jesus was conceived by the Holy Spirit and born of a virgin. Jesus was tempted in all ways as we are, but he is without sin (Heb. 4:15). It is very important that the first three Gospel accounts—the Synoptic Gospels—all include Jesus’ temptation in the wilderness. Each one has a different emphasis, but they all have the same point: Jesus defeats the tempter. This is the Great High Priest that we all need—one who is holy from the beginning, one who defeats the tempter, one who gives grace to cover and to conquer all sin.