Re-baptism
Re-baptism, sometimes called Anabaptism, refers to the unbiblical practice of having one person Baptised several times.
As "True Baptism"
Some Christian denominations have practiced re-baptism in belief that the first baptism a person received was false.
Donatism
The Donatists, a schismatic group within Early Christianity, believed that if a person had been baptised by a priest who later went on to apostatize, that baptism became invalid. They were condemned by the rest of the Early Church, who stated that Baptism only required the righteous mediation of the Holy Spirit, not the mediation of a priest.
Anabaptism
The Anabaptists, a radical protestant denomination which rejected infant baptism, believed that when a person joined their church, that person must be re-baptised as infant baptism did not count.
This belief is sometimes carried into Evangelical or Baptist theology.
As Ritual Baptism
Some non-Christian religions practice Baptism as a way to achieve purity.
Second Temple Jews
Some Second Temple Jews practiced ritual bathing as a way to wash away sins. They would enter a ritual bath after committing a non-kosher act such as touching a dead body or an unclean object.
Mandaeans
The Mandaeans, a Jewish neo-gnostic sect which claims to be descended from the followers of John the Baptist, practises ritual baptism.
Biblical view
Most Reformed Christians view re-baptism as unbiblical, citing these verses from the Bible:
"One Lord, one faith, one baptism." - Ephesians 4:5
"Peter said to them, ‘Repent, and be baptized every one of you in the name of Jesus Christ so that your sins may be forgiven; and you will receive the gift of the Holy Spirit. For the promise is for you, for your children, and for all who are far away, everyone whom the Lord our God calls to him.’" - Acts 2:38-39
"Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? Therefore we have been buried with him by baptism into death, so that, just as Christ was raised from the dead by the glory of the Father, so we too might walk in newness of life." - Romans 6:3-4
