The Kingdom Come

Why does Jesus and the Bible sometimes refer to Him as the Son of God and other times as the Son of Man? Is one expressing Jesus' deity whereas the other expressing His humanity?

Let's first look at the title, Son of God. In the Christian understanding, Jesus is seen as the unigenitus Dei Filius or the only begotten Son of God, whereas general humanity may be considered "sons of God" generically since God is called The Father. An example of the general use can be found in Gen 6:1-2 where it is said the "sons of God" copulated with the daughters of men. This verse is often interpreted as the "sons of God" being either angels or righteous men. The dominant interpretation is that "sons of God" indicate, humanity within the covenantal relationship with God, or specifically in Gen 6:1-2, the offspring of Seth rather than the offspring of Cain. The view that "sons of God" relates to angels is typically held by heretical or cultic groups, such as the Jehovah's Witnesses.(source #1, source #2 see also: Job 1:6, Job 38:7, Psalm 29:1)

So, the title Son of God in Jesus' case is to identify Him as the unique or as said, "only begotten" Son of God as opposed to a mere equal with the "sons of God".

The title of Son of Man can also be contrasted as idiom for general humanity; especially when used as "sons of men". (Bible refs). Specifically, we see where God is contrasted as NOT being part of humanity or a "son of man".

"God [is] not a man, that He should lie, Nor a son of man, that He should repent. Has He said, and will He not do? Or has He spoken, and will He not make it good?" -- Numbers 23:19

So, isn't this a contradiction to the claim that Jesus is deity, Jesus is God? Why would Jesus use this label for Himself? Is He using it simply to be humble?

Let's tie it all together now. Understanding that both expressions; sons of God and sons of man/men can indicate generically, humanity or mankind but specifically when Jesus uses the terms they act as definite articles, referring to Him alone. We must consider what is being conveyed. Perhaps the issue becomes clear when we look at 1 Corinthians 15:45 --

"And so it is written, 'The first man Adam became a living being.' The last Adam became a life-giving spirit."

As Adam is the representative of mankind, in the flesh, Jesus is the last Adam or the representative of the new mankind, in the spirit. Thus, both expressions and titles of Jesus as the "Son of God" and the "Son of Man" are NOT contradictions (although it may be a paradox at first). It is a beautiful and amazing way to capture the fully man/fully God nature of Jesus (see Hypostatic union)