"Thou Forgavest the Wickedness of my Heart" by St Cyril of Jerusalem

St Cyril of Jerusalem (313-386) A.D. Source

"God is loving to man, and loving in no small measure. For say
not, I have committed fornication and adultery: I have done
dreadful things, and not once only, but often: will He forgive?
Will he grant pardon? Hear what the Psalmist says: How great
is the multitude of Thy goodness O Lord! Thine accumulated
offenses surpass not the multitude of God's mercies: thy
wounds surpass not the great Physician's skill.

Only give thyself up in faith: tell the Physician thine ailment:
say thou also, like David: I said I will confess me my sin unto
the Lord: and the same shall be done in thy case, which he
says forthwith: And Thou forgavest the wickedness of
my heart." Cathecesis II.6 Source

Therapy of Spiritual Illnesses by Dr Jean Claude-Larchet vol 2 p.24,
Translated by Fr Kilian Sprecher, 3 volume boxed set Copyright
@2012 Alexander Press, Montreal, Quebec, Canada 

Look here