A sign in Scripture refers to an external act that points to an internal change of heart.
Adherants of reformed theology believe that circumcision and baptism are both signs and seals of the covenant of grace.
Gen 17:11 ~ You are to undergo circumcision, and it will be the sign of the covenant between me and you.
Here, Abraham undergoes circumcision, which is a sign: an external act that points to God's covenant.
- Gen 9:13, the rainbow a sign of the covenant between God and the earth.
- Ex 3:12, worshipping God a sign that God is with Moses.
- Ex 8:23, plagues a miraculous sign that there is a distinction between the Egyptians and the Hebrews.