Of these conditions, one flows from the infinite holiness of His own nature, namely: contrition or repentance. The other, which is judicial absolution from sin, implying previous confession of it, is imposed by the revealed law of God, and is therefore a divine command obliging all—popes and bishops, priests and people. Let us deal with these separately.
 John i, 8.
 James iii, 2.
 Prov. xxiv, 16.
 Ps. v, 6.
 Wisd. xiv, 9.
 Ezech. xviii, 24.
 Rev. xxi, 8.
 James i, 15.
 Ecclus. xxi, 2.
The necessity of repentance as the essential condition for the sinner obtaining God’s forgiveness is plainly taught both in the Jewish and Christian dispensations.
Prophets and penitents throughout the Old Testament bear evidence to this truth. The words of the Psalms of David, the exhortations of Jeremias and Isaias to the people of God to be converted, have become household words in our books of piety, exciting the soul in sin to arise and go to the God of mercy.
The New Dispensation was ushered in by the Forerunner of Christ preaching the Gospel of Repentance: “Do penance, for the kingdom of God is at hand.” Our Lord announces His own mission to be to call sinners to repentance: “Unless you all do penance, you shall all likewise perish.” He sent His Apostles that “penance and remission of sin should be preached in His name among all nations.” And, while on earth, Jesus sent them, two and two, to preach that “men should do penance.”
And, after the ascension of the “Saviour whom God hath exalted with His right hand to give penitence to Israel, and remission of sins," the Apostles proclaimed the same truth. Peter’s very first sermon is: “Do penance and be baptized, every one of you." He, on the occasion of the cure of the lame man, preaches: “Be penitent and be converted, that your sins may be blotted out." The same Apostle writes: “The Lord beareth patiently for your sake, not willing that any should perish, but that all should return to penance." St. Paul, in like manner. “God commandeth all men, everywhere, to do penance." And again: “The benignity of God leadeth thee to penance."