Theme: The LORD is faithful to his promises, he shows grace to his people; praise and thank him with joyful obedience

Circumcision, Baptism and unbelief
Circumcision was a sign and a seal of the covenant of grace which God made with Abraham. It was meant to be done for every male in every generation (Genesis 17:11) in order to mark the people out as belonging to God. Male members represented the whole household.
For old covenant believers, if you were not circumcised, you were not considered to be part of God’s people (Genesis 17:14). Passing on the sign of circumcision to male offspring was thus an important act of faith. For believers to refuse to do so was considered a sinful act of unbelief and resulted in God's wrath (see Exodus 4:24-26). Because baptism has replaced circumcision as the sign of the covenant (Colossians 2:11-14; HC Question 74; BC Article 34), refusing to baptise the children of believers should likewise be seen as an act of unbelief and a sin (cf. WCF 28.4-5).