To suffer death was the immediate end of the interposition of Christ. The principal end of his undertaking was to right the honour of God, and glorify his attributes in the recovery of the creature; but the immediate end was to suffer, because this was the only way to bring about that end which was principally aimed at in Christ’s interposition, and God’s determination concerning him. Death being denounced as the punishment of sin, Christ interposeth himself for our security, with a promise to bear that punishment in our stead for the procuring our exemption from it; therefore, what punishment was of right to be inflicted on man for the breach of the law, was, by a gracious act of God, the governor of the world and guardian of his laws, transferred upon Christ, as putting himself in our stead. His first interposition was for the same end with his death, but his death was evidently for our sins. It was for them ‘he gave himself,’ Gal. 1:4; they were our sins which ‘he bare in his own body on the tree,’ 1 Peter 2:24; ‘for our iniquities he was wounded, and for our transgressions he was bruised,’ Isa. 53:5; our health was procured by his stripes, and therefore intended by him in his first engagement. He offered his person in our stead, which was able to bear our sin, and afford us a righteousness which was able to justify our persons; he offered himself to endure the curse of the law in his own body, and fulfil the righteousness of the law in his own person; he would be united with us in our nature, that he might make the sins of our nature his own in suffering for them, and give to us what was his, by taking to himself what was ours; he took our stripes that we might receive his medicine. This, therefore, being the end of his first undertaking, was necessary to be performed; for Christ is not yea and nay, 2 Cor. 1:19, one time of one mind, and another time of another, but firm and uniform in all his proceedings, without any contradiction between his promise and performance.
The Complete Works of Stephen Charnock, 5:10.