But we see him who for a little while was made lower than the angels, namely Jesus, crowned with glory and honor because of the suffering of death, so that by the grace of God he might taste death for everyone. – Hebrews 2:9
God cannot die and the salvation of sinful men depends entirely on the death of a perfect Substitute. Since no man is righteous and without sin (Romans 3:10; Ecclesiastes 7:20), God Himself came, in grace, to be our perfect Substitute, that we might glorify and enjoy Him forever. As Hebrews 2:9 says, we see Jesus, who is God, for a little while made lower than the angels—this is the Christmas story. This is the incomprehensible wonder of the incarnation and suffering and exaltation of Christ. It is all a testimony of the grace of God. Its purpose was so that He who is God “might taste death,” so that we who are sinners might enjoy eternal life.
B. B. Warfield said it well: “The Son of God as such could not die; to Him belongs by nature an ‘indissoluble life’ (7:16). If He was to die, therefore, He must take to Himself another nature to which the experience of death were not impossible (2:17).” This is an encompassing reason for the incarnation, the purpose for which Christ came. Jesus said, “Truly, truly, I say to you, unless a grain of wheat falls into the earth and dies, it remains alone; but if it dies, it bears much fruit. … Now is my soul troubled. And what shall I say? ‘Father, save me from this hour’? But for this purpose I have come to this hour” (John 12:24–27). “For this purpose,” says Jesus, He came to earth and came to the hour of His death. There would be no hope of any other lasting benefit of His coming without His death. Therefore, we can summarily agree with Robert Culver, “The Passion and death of Christ … were designated by Jesus as the chief reasons for the incarnation.”
Why the incarnation? Why the God-man? So that He who is God could die in the place of guilty sinners.