Sacrament

The oath of allegiance taken by Roman soldiers; hence, a sacred ceremony used to impress an obligation; a solemn oath-taking; an oath.

The pledge or token of an oath or solemn covenant; a sacred thing; a mystery.

One of the solemn religious ordinances enjoined by Christ, the head of the Christian church, to be observed by his followers; hence, specifically, the eucharist; the Lord's Supper.

To bind by an oath.