Nicæa I: canon XII

Those who have been called by grace, have given evidence of first fervour and have cast off their [military] belts, and afterwards have run back like dogs to their own vomit, so that some have even paid money and recovered their military status by bribes -- such persons shall spend ten years as prostrators after a period of three years as hearers. In every case, however, their disposition and the nature of their penitence should be examined. For those who through their fear and tears and perseverance and good works give evidence of their conversion by deeds and not by outward show, when they have completed their appointed term as hearers, may properly take part in the prayers, and the bishop is competent to decide even more favourably in their regard. But those who have taken the matter lightly, and have thought that the outward form of entering the church is all that is required for their conversion, must complete their term to the full.