This question was brought to me recently. It was one of those questions I just couldn’t answer off the top of my head. Other questions followed closely behind this one like, “If Jesus was the son of Mary, he would have inherited sin from her” and “Was Mary purified before the birth of Jesus to make his sinless nature possible?” It was one of those ‘hard to answer’ questions that usually get lost somewhere in the deep recesses of your mind before you decide to try to address it. Sort of like skipping rocks across a still pond. The rock skips two, three, four times and then it disappears forever into the deep water never to be seen again. But, I think this question deserves an answer.
Original sin is that sin which we inherit from Adam. Its existence is evidenced by our own experience. Everyone feels a ‘bent’ toward sin. Sin is in our nature. This depravity, or tendency to sin, is passed down to every human being from our common father, Adam. Romans 5:12 "Therefore, just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned." Sin came through Adam, redemption comes through Jesus Christ.
Jesus was born without sin and he lived his entire life sinless. Had he not, there would be no redemption possible for us. How could he be sinless if he had a sinful mother? Is it not possible that the sin nature is passed down through the father. The Bible references to the descendents as being in the “loins of their fathers.” Because Jesus had no earthly biological father no sin nature was passed down to him. Col. 2:9 says "For in Him dwells all the fullness of deity in bodily form." Jesus had two complete natures. He was both fully human and fully divine.
The question about the sinless Christ is not explicitly answered in the Bible. We know he had no sin, we just don’t know exactly how that was accomplished.
Another explanation is that Mary was purified, indeed deified, so that Christ could be born sinless. There is no evidence at all of this. In fact, this idea violates the truth in the Word of God. The Bible teaches that there is only one God. That entity has three separate persons: The Father, The Son and The Holy Spirit. To add Mary to the triune God is heretical. Jesus said, “I and my Father are one.” Mary was chosen to give birth to Christ and her conception was supernatural but she is still only fully human.
It’s such a good question to which I can only surmise an answer. There are some things God chose not to reveal to us. Now we see through a glass darkly, perhaps one day we will see clearly.