That God the Son took upon Himself a real human nature is a crucial doctrine of historic Christianity. The great ecumenical Council of Chalcedon in A.D. 451 affirmed that Jesus is truly man and truly God and that the two natures of Christ are so united as to be without mixture, confusion, separation, or division, each nature retaining its own attributes.
The true humanity of Jesus has been assaulted chiefly in two ways. The early church had to combat the heresy of docetism, which taught that Jesus did not have a real physical body or a true human nature. They argued that Jesus only "seemed" to have a body but in reality was a phantom sort of being. Over against this, John strongly declared that those who denied that Jesus came truly in the flesh are of the Antichrist.
The other major heresy the church rejected was the monophysite heresy. This heresy argued that Jesus did not have two natures, but one. This single nature was neither truly divine nor truly human but a mixture of the two. It was called a "theanthropic" nature. The mono-physite heresy involves either a deified human nature or a humanized divine nature.
Subtle forms of the monophysite heresy threaten the church in every generation. The tendency is toward allowing the human nature to be swallowed up by the divine nature in such a way as to remove the real limitations of Jesus' humanity.
We must distinguish between the two natures of Jesus without separating them. When Jesus hungers, for example, we see that as a manifestation of the human nature, not the divine. What is said of the divine nature or of the human nature may be affirmed of the person. On the cross for example, Christ, the God-man, died. This, however, is not to say that God perished on the cross. Though the two natures remain united after Christ's ascension, we must still distinguish the natures regarding the mode of His presence with us. Concerning His human nature, Christ is no longer present with us. However, in His divine nature, Christ is never absent from us.
Christ's humanity was like ours. He became a man "for our sakes." He entered into our situation to act as our Redeemer. He became our substitute, taking upon Himself our sins in order to suffer in our place. He also became our champion, fulfilling the law of God on our behalf.
In redemption there is a twofold exchange. Our sins are imparted to Jesus. His righteousness is imparted to us. He receives the judgment due to our imperfect humanity, while we receive the blessing due to His perfect humanity. In His humanity Jesus had the same limitations common to all human beings, except that He was without sin. In His human nature He was not omniscient. His knowledge, though true and accurate as far as it went, was not infinite. There were things He did not know such as the day and the hour of His return to earth. Of course in His divine nature He is omniscient and His knowledge is without limit.
As a human being Jesus was restricted by time and space. Like all human beings He could not be in more than one place at the same time. He sweated. He hungered. He wept. He endured pain. He was mortal, capable of suffering death. In all these respects He was like us.