What is a sacrament? – Shorter Westminster Catechism

A sacrament is an holy ordinance instituted by Christ ; wherein, by sensible signs, Christ, and the benefits of the new covenant, are represented, sealed, and applied to believers.

Shorter Westminster Catechism

How do the sacraments become effectual means of salvation? – Shorter Westminster Catechism

Which are the sacraments of the New Testament? – Shorter Westminster Catechism