The unbelieving receive the external sign or sacramentum; but the believing receive in addition, although invisibly, the reality represented by the sign, the res sacramenti.
The time requisite for the several degrees is unknown, and may have been determined by the Patres, who conferred them in a solemn ceremony called Sacramentum, in which the initial step was an oath never to divulge what should be revealed, and for which the mystic had been specially prepared by lustral purification, prolonged abstinence, and severe deprivations.
The Latin word sacramentum originally meant any bodily or sensible thing, or an action, or a form of words solemnly endowed with a meaning and purpose which in itself it has not.
Roman recruits when they took the sacramentum, or oath of fealty, were tattooed with the "sign" or "seal."
Its antiquity is attested by the symbol and formula used in its procedure, the lance (hasta) as the sign of true ownership, the oath or wager (sacramentum), the ancient formula for recovery of property or assertion of liberty.
The commune (communia, communa, communio, communitas, conjuratio, confoederatio) was formed by an oath of mutual help (sacramentum, juramentum communise).