How is it signified and sealed to you in Holy Baptism that you have part in the one sacrifice of Christ on the cross?

Heidelberg Catechism

~Baptism

Question 69. How is it signified and sealed to you in Holy Baptism that you have part in the one sacrifice of Christ on the cross?

Answer. Thus: that Christ instituted this outward washing with water [1] and joined to it this promise, that I am washed with His blood and Spirit from the pollution of my soul, that is, from all my sins, as certainly as I am washed outwardly with water, whereby commonly the filthiness of the body is taken away.[2]

[1] Mt 28:19-20; Acts 2:38;
[2] Mt 3:11; Mk 1:4; Jn 1:33; Acts 2:38; Rom 6:3-4; 1 Pt 3:21