But why was it required that our Saviour should be God? I answer, 1. Because none can save souls, nor satisfy for sin alone: "There is none, (says the psalmist) that can by any means redeem his brother nor give to God a ransom for him.--But God will redeem my soul from the power of the grave."(Psalm 49:7) 2. Because the satisfaction which is made for sin, must be infinitely meritorious. An infinite wrath cannot be appeased, but by an infinite merit; and hence our Saviour must needs be God, to the end that His obedience and sufferings might be of infinite worth. 3. Because the burden of God's wrath cannot be endured by a finite creature; Christ therefore must be God, that He might abide the burden, and sustain the manhood by His Divine Power. 4. Because the enemies of our salvation were too strong for us: how could any creature overcome Satan, death, hell, and damnation? This required the power of God: there is none but God that could destroy "him that had the power of death, that is the devil."
As Christ is God, so he is true man. He was born as man, and bred as man, and fed as man, and slept as man, and wept as man, and sorrowed as man, and suffered as man, and died as man; therefore he is man. But more particularly, Christ had a human body. "Wherefore when he came into the world, he said, sacrifice and offerings You would not, but a body You prepared for me." (Hebrews 10:5) Christ had a human reasonable soul. "My soul is heavy unto death." (Mark 14:33-34) And again, "Father, into Your hands I commend my Spirit." (Luke 23:46) Christ had all the properties that belong either to the soul or body of a man: nay more, Christ had all the infirmities of our nature, sin only excepted; as cold, and heat, and hunger, and thirst, and weariness, and pain, and the like.
But why was it required, that our Savious should be man? I answer, 1. Because our Saviour must suffer and die for our sins, which the Godhead could not do. 2. Because our Saviour must perform obedience to the law (for us), which was not agreeable to the lawgiver; the Godhead certainly is free from all manner of subjection. 3. Because our Saviour must satisfy the Justice of God in the same nature wherein it was offended. 4 Because by this means we might have free access to the throne of grace, and might find help in our necessities, having such an High Priest, as was in all things tempted like unto us, and was acquainted wit our infirmities in His own person. (Hebrews 4:14-16)
From the union of these two natures, believers derive the inestimable privilege of being themselves personally united to Christ, If you are united to Christ, you have all Christ! (Colossians 2:9-10): You are one with Him in His nature, in His name: you have the same image, grace and Spirit in you as He has; the same precious promises, the same access to God by prayer as He: you have the same Love of the Father, all that He did or suffered, you have a share in it: you have His live and death; all is yours. So on your pare, He has you wholly, your nature, your sins (while not being a sinner), the punishment of your sin, your wrath, your curse, your shame: yes, all that you are is for Him (I Corinthians 6:20). "My Beloved is mine, and I am His." (Song of Solomon 2:16)