The fact that Christ has experienced weakness and suffering is critical to His high priesthood. Like the Old Testament high priests, He can have compassion on the ignorant and wayward because He Himself has worn weakness (Heb 5:2). While He never sinned, He understands how and why we do, and He understands this because He had to offer up prayers and supplications with strong crying and tears (Heb 5:7). He did these things according to His human nature, but He did them as the God-man.
Last week we explored the concept of Jesus Christ as the God-man. We learned that He is one person in two natures. Each nature is complete, possessing all the essential properties of that nature. The properties of each nature communicate to the person but not to the other nature. Consequently, paradoxical statements may be applied to the person in view of the two natures. The babe in the manger was omnipotent according to His divine nature but weak according to His human nature. He was omniscient according to His divine nature but able to learn according to His human nature. He was omnipresent according to His divine nature but spatially localized according to His human nature.
Most puzzling of all, we saw that the person can be designated by the names of one nature while acting according to the properties of the other. Hebrews 13:8 states that Jesus (His human name) is immutable (a divine property). Matthew 1:23 names Him Immanuel (God with us, a divine name) while speaking of His gestation and birth (human processes). In Acts 20:28, Paul, referring to Christ, says that God (a divine name) purchased the church with His own blood (a human property).
If pressed, we will want to limit and qualify these descriptions. We are eager to avoid misunderstandings, such as the conclusion that the divine nature could be tempted or that the human nature is eternal. We know that if we go an inch too far in our affirmations, we shall precipitate ourselves into heresy. The problem is that if we stop an inch short we shall also plunge into heresy. What we affirm with clarifications and qualifications we must never deny.
Beginning with His incarnation, the acts of Jesus Christ were all done by the one person. Neither His divine nature nor His human nature ever acted separately from His person. Everything He did must be ascribed to His person, which is both divine and human. Whatever was done according to the human nature was nevertheless done by the divine person, and vice versa.
This joining of two natures in one person is called the hypostatic union. On the scale of doctrinal importance, the hypostatic union stands right at the top. It is essential to the gospel and to the Christian faith. To deny it is to deny Christianity itself. It is a fundamental of the faith.
Like other fundamentals, the hypostatic union can function as a theological paradigm. In other words, we can use it to discern what answers we should give when asked unanticipated questions. In this case, two examples will illustrate the kind of applications we might make.