Johann Gerhard lists several practical uses of the biblical teaching concerning the Two Natures in our Lord Jesus. The quote below comes from his first reason.
Bernard writes very beautifully: “From God and man a bandage was made to heal all our infirmities, and the Holy Spirit like a pestle sweetly mixes together (conjoins) these drugs in the womb of Mary.” No other medicine could heal the lethal wounds of our soul. Our first parents were seduced through the serpent (Gen. 3:2). He was not just a natural serpent, but in him hid the serpent of hell who injected the lethal poison of sin in them. They spread that into all their descendants and into the entire human race. The expulsion of this poison and the healing of our corrupt nature did not require a common nature but the sort to be prepared for us from the divine and human natures in Christ. Through his extreme malice the devil had infected the nature of man; therefore God wished to show us His immense goodness in healing us. The devil had expended all his craft in seducing man; therefore God applied His greatest wisdom to prepare a medicine for our fall. The poison of the fall introduced into us not only temporal death but also eternal death; therefore help could be prepared for us not through a worldly medicine but through a heavenly and life-giving medicine. The poison was from hell; therefore the antidote had to come from heaven. With his poison, the basilisk of hell had infected the entire human nature in our first parents; therefore the Son of God assumed the whole and perfect human nature to deliver the whole man from this poison. He whom the serpent has wounded fatally cannot prepare a medicine for himself. Thus we could not have prepared a cure for ourselves after we were struck by the infernal serpent. However, in the womb of Mary, God prepared the most precious medicine against those stings by uniting personally, through the operation of the Holy Spirit, the divine and human natures in Christ so that He would be our physician and our medicine, healing the wounds of our soul, soothing our pains, restoring our health.
Gerhard, Johann Theological Commonplaces: Exegesis IV: On Christ 143