Justification is being declared legally righteous by God. This justification is received by faith alone without any ceremony/baptism (Rom. 4:1-6), in the work of Christ fulfilling the Law in his earthly ministry (1 Pet. 2:22), and his removing of sin by his sacrifice. Justification is a gift from God (Rom. 3:24) and is received apart from the works of the Law (Rom. 3:28; Gal. 2:21).
See also What is Justification?.