In the Early Christian Church absolution for sin was granted after confession and absolution; reconciliation was followed by readmission to the Eucharist. Absolution was granted once in a lifetime, and at set seasons of the year. Public penance did not necessarily include a public avowal of sin, but was decided by the confessor, and was to some extent determined by whether or not the offense was sufficiently open or notorious to cause scandal to others. Oakley points out that recourse to public penance varied both in time and place, and was affected by the weaknesses of the secular law. The ancient praxis of penance relied on papal decrees and synods, which were translated and collected in early medieval collection. Little of those written rules, however, was retained in the later penitentials.
The earliest important penitentials were those by the Irish abbots Cummean (who based his work on a sixth-century Celtic monastic text known as the Paenitentiale Ambrosianum), Columbanus and Archbishop of Canterbury, Theodore of Tarsus. Most later penitentials are based on theirs, rather than on earlier Roman texts. The number of Irish penitentials and their importance is cited as evidence of the particular strictness of the Irish spirituality of the seventh century. Walter J. Woods holds that "ver time the penitential books helped suppress homicide, personal violence, theft, and other offenses that damaged the community and made the offender a target for revenge."
According to Thomas Pollock Oakley, the penitential guides first developed in Wales, probably at St. David's, and spread by missions to Ireland. They were brought to Britain with the Hiberno-Scottish mission and were introduced to the Continent by Irish and Anglo-Saxon missionaries.
As priests heard confessions, they began to compile unofficial handbooks that dealt with the most confessed sins and wrote down set penances for those sins. Penances would vary given both the severity of the offense and the status of the sinner; such that the penance imposed on a bishop would generally be more severe than that imposed on a deacon for the same offense. For stealing, Cummean prescribed that a layman shall do one year of penance; a cleric, two; a subdeacon three; a deacon, four; a priest, five; a bishop, six.
The list of various penitential acts imposed on the sinner to ensure reparation included more or less rigorous fasts, prostrations, deprivation of things otherwise allowable; also alms, prayers, and pilgrimages. The duration was specified in days, quarantines, or years. Gildas lists the penance for an inebriated monk, "If any one because of drunkenness is unable to sing the Psalms, being stupefied and without speech, he is deprived of dinner."