What is a sacrament?

A sacrament is a holy ordinance instituted by Christ in his church, to signify, seal, and exhibit unto those that are within the covenant of grace, the benefits of his mediation; to strengthen and increase their faith, and all other graces; to oblige them to obedience; to testify and cherish their love and communion one with another; and to distinguish them from those that are without.

Proofs

• A sacrament is a holy ordinance instituted by Christ in his church, (Genesis 17:7, 10; Exodus 12; Matthew 26:26–28)
• to signify, seal, and exhibit (Romans 4:11; 1 Corinthians 11:24–25)
• unto those that are within the covenant of grace, (Romans 15:8; Exodus 12:48)
• the benefits of his mediation; (Acts 2:38; 1 Corinthians 10:16)
• to strengthen and increase their faith, and all other graces; (Romans 4:11; Galatians 3:27)
• to oblige them to obedience; (Romans 6:3–4; 1 Corinthians 10:21)
• to testify and cherish their love and communion one with another; (Ephesians 4:2–5; 1 Corinthians 12:13)
• and to distinguish them from those that are without. (Ephesians 2:11–12; Genesis 34:14)