The necessity of approbation, especially for administering the Sacrament of Penance, was expressly decreed by the Council of Trent, so that, except in the case of imminent death, the absolution by a priest not approved would be invalid. This approbation for the Sacrament of Penance is the judicial declaration of the legitimate superior that a certain priest is fit to hear, and has the faculties to hear, the confession of his subjects.
By bishop is meant also his vicar general, or the diocesan administrator during the vacancy of a see, also any regular prelate having ordinary jurisdiction over a certain territory. This approbation may be given orally or in writing, and may be given indirectly, as when, for instance, priests receive power to choose in their own diocese an approved priest of another diocese for their confessor. The bishop may wrongfully but validly refuse his approbation, without which no priest may hear confessions.
A confessor's jurisdiction may be restricted to various classes of persons, e. g. to children, or to men, without the right to hear women. A special approbation is required to hear nuns or women of religious communities, and this extends with modifications to all communities of recognized sisterhoods.