A most important article here as it is crucial to your and my salvation! He was very God of God and also very man of man. If you deny one of these things, then you do NOT have salvation as He cannot be our substitute as the soul that sins must die. (God would not punish any other for the sins of man.) And only God of God could and can withstand eternal hell which was the payment for sin. Any buy-in into the world that denies the Holy Spirit's conceiving in the womb of the virgin Mary completely illuminates and denies salvation.
Meaning: John puts this very truth before us. "The Word was God and the Word became flesh and dwelt among us..." The more one dives into this the more one is lost and the more questions we seem to have. The carnal mind will never ever grasp it and it is a matter of faith that we believe this wonder. The "natural" Son of God assumes and takes upon Himself all the essential characteristics that make us man. The sum of those characteristics He became. He did this that He could take upon Himself our sin and make satisfaction for them. That which we could not do...God satisfies in our likeness and does so except without sin. A complete human nature without the embellishment we often see around Christmas time. His experience is you and me!
Manner: But how? It is at this point that we bow our heads in the unexplainable where God and man meet each other. The eternal, spiritual, and the natural. We were conceived in sin according to the will of man. God in the miracle of His grace then provides and then our Lord Jesus Christ takes upon Himself the very nature of man and does so willingly as He becomes man and becomes a willing sacrifice. The 2nd nature takes upon the nature upon Himself and personalizes it. Two natures into ONE person. Something you won't understand and I will not understand as we both only know one nature in one person. Two realms that are different coming together....a complete wonder of God's grace. The fulfillment of the promise! We are born and conceived in sin with nothing good and there is no salvation even possible in ourselves.
Benefit: Our Lord Jesus Christ is born as the spotless Lamb of God who is the PERFECT subject in and of Himself to make complete satisfaction for us. He is the SAVIOR! Christ the Lord!