It is not an incidental point—our salvation actually depends on it. In order to serve as a sin sacrifice, the Lord Jesus had to be a true human being, and the Lord Jesus had to be sinless. If Jesus were not truly human, the sacrifice could not have been the work of our representative priest (Heb. 4:15). And if Jesus were not entirely sinless, then like the Levitical priests, he would have had to make an offering for his own sin first. This means Jesus would not have been in a position to die for ours (Heb. 7:27). Jesus could not be the sacrifice for us unless he was a sacrificial victim entirely without blemish (1 Pet. 1:19). And so—for the sake of our salvation—it was necessary to find a man who was a true man, and yet who was without sin.
Read Doug Wilson’s excellent post of the virgin birth here: