God must die on the cross. Only thus can human hearts be pierced and turned away from self and sin; only thus can mankind apprehend the true identity and nature of their Creator and be converted to the path of salvation. It is the divine love, manifested in the humility and death of the Son, that transforms sinners and brings them everlasting life.
But the sum of all is that God the Lord surrendered His own Son to death on the Cross for the fervent love of creation. … This was not, however, because He could not have redeemed us in another way, but so that His surpassing love, manifested hereby, might be a teacher unto us. And by the death of His only-begotten Son He made us near to Himself. Yeah, if He had had anything more precious, He would have given it to us, so that by it our race might be His own.
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Source: Isaac of Nineveh, Part I.71, p. 492
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