Isaac of Stella (? – about 1171), Cistercian monk Sermon 11 (breviary translation)
“Who but God alone can forgive sins?" (Mk 2:7)
The prerogative of receiving the confession of sin and the power to forgive sin are two things that belong properly to God alone. We must confess our sins to him and look to him for forgiveness. Since only he has the power to forgive sins, it is to him that we must make our confession.
But when the Almighty, the Most High, wedded a bride who was weak and of low estate, he made that maid-servant a queen. He took her from her place behind him, at these feet, and enthroned her at his side. She had been born from his side, and therefore he betrothed her to himself (Gn 2:22; Jn 19:34). And as all that belongs to the Father belongs also to the Son because by nature they are one (Jn 17:20), so also the bridegroom gave all he had to the bride and he shared in all that was hers.
He made her one both with himself and with the Father… And so the bridegroom is one with the Father and one with the bride. Whatever he found in his bride alien to her own nature he took from her and nailed to his cross when he bore her sins and destroyed them on the tree. He received from her and clothed himself in what was hers by nature and gave her what belonged to him as God…
Thus, sharing as he did in the bride's weakness, the bridegroom made his own her cries of distress, and gave his bride all that was his. Therefore, she too has the prerogative of receiving the confession of sin and the power to forgive sin, which is the reason for the command, “Go, show yourself to the priest.” (Mk 1:44)