God deals with Sin

"God has always said that sin is to be punished, that his holy wrath is upon it, and that he cannot deal with sin in any other terms. And he has done exactly what he promised. On the cross he is doing it publicly. There he is, once and for all, at the central point of history, pouring out His wrath upon the sins of man in the body of His own Son. He is striking him, He is smiting him, he is condeming him to death. He dies, and his blood speaks. It is God's punishment of sin and evil. It is a mighty declaration that God has done what he always said he would do, namely, that he would punish sin, and the wages of sin is death. And there you see it happening upon the cross." - Martyn Lloyd - Jones (The Cross: God's Way of Salvation p 163)

That about sums up what was happening on that "GOOD Friday" And as Mrs C F Alexander puts it in her hymn there was only one person that could do this - Jesus!

There was no other good enough
To pay the price of sin;
He only could unlock the gate
Of heaven and let is in