Baptism
Ephesians 4:5
One Lord, one faith, one baptism,
KJV
When you become saved, you are sealed with the Holy Spirt. It says in Ephesians 1:13-14 KJV "13 In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, 14 Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory." This is the one baptism that is highlighted in Ephesians 4:4-6 KJV "4 There is one body, and one Spirit, even as ye are called in one hope of your calling; 5 One Lord, one faith, one baptism, 6 One God and Father of all, who is above all, and through all, and in you all."