Baptism

Commanded "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit," (Matthew 28:19)
An element of invitation "Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit." (Acts 2:38)
A response of believers "He who believes and is baptized will be saved; but he who does not believe will be condemned." (Mark 16:16)
"Then those who gladly received his word were baptized; and that day about three thousand souls were added to them." (Acts 2:41)
"Now as they went down the road, they came to some water. And the eunuch said, “See, here is water. What hinders me from being baptized?” Then Philip said, “If you believe with all your heart, you may.” And he answered and said, “I believe that Jesus Christ is the Son of God.”" (Acts 8:36-37)
A picture of our union with Christ "buried with Him in baptism, in which you also were raised with Him through faith in the working of God, who raised Him from the dead." (Colossians 2:12)
A physical declaration of a spiritual reality "For by one Spirit we were all baptized into one body— whether Jews or Greeks, whether slaves or free—and have all been made to drink into one Spirit." (1 Corinthians 12:13)
" What shall we say then? Shall we continue in sin that grace may abound? Certainly not! How shall we who died to sin live any longer in it? Or do you not know that as many of us as were baptized into Christ Jesus were baptized into His death? Therefore we were buried with Him through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life. For if we have been united together in the likeness of His death, certainly we also shall be in the likeness of His resurrection, knowing this, that our old man was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin." (Romans 6:1-6, NKJV)