Saved by God's mercy
Titus 3:5 Not by works of righteousness which we have done, but according to his mercy he saved us, by the washing of regeneration, and renewing of the Holy Ghost.
Baptism has the power to wash away sin
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
God's commission on baptism:
Matthew 28:19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
Matthew 28:20 Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
Baptism of the Holyspirit brings about the gifts of the Holyspirit:
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
It is baptism that brings us together as one body of Christ:
1 Corinthians 12:13 For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit.
Colossians 1:18 And he is the head of the body, the church: who is the beginning, the firstborn from the dead; that in all things he might have the preeminence.
Ephesians 4:4 There is one body, and one Spirit, even as ye are called in one hope of your calling.
1 Corinthians 3:16 Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?
Hebrews 3:6 But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end.