Where did the dismissal of catechumens come from?
The dismissal of the catechumens is a liturgical rite that is done any time catechumens are present at Mass: When [catechumens] are present with the congregation of the faithful, they must normally be gently dismissed before the Eucharistic Celebration begins. (OCIA 75.3) The practice of dismissing the catechumens before the liturgy of the Eucharist begins …