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(All quotations from the King James Version unless stated otherwise).
There is an example of a second baptism in Acts 19:
Acts 19:1 And it came to pass, that, while Apollos was at Corinth, Paul having passed through the upper coasts came to Ephesus: and finding certain disciples, 2 He said unto them, Have ye received the Holy Ghost since ye believed? And they said unto him, We have not so much as heard whether there be any Holy Ghost. 3 And he said unto them, Unto what then were ye baptized? And they said, Unto John’s baptism. 4 Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus. 5 When they heard this, they were baptized in the name of the Lord Jesus. 6 And when Paul had laid his hands upon them, the Holy Ghost came on them; and they spake with tongues, and prophesied. 7 And all the men were about twelve.
Baptism is valid only if we believe the gospel which was preached by Jesus and the apostles at the time of baptism.
Mark 16:15 And he said unto them, Go ye into all the world, and preach the gospel to every creature. 16 He that believeth and is baptized shall be saved...
If we are baptised believing a gospel and doctrine which we later find to be false or severely inadequate, a second baptism becomes necessary.
Galatians 1:6 I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel... 8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
2 Corinthians 11:4 For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear with him.
There are many churches and consequently many false gospels.
There is no restriction on how often we can be baptised.
The gospel received must agree with what we find in the Bible.
Acts 17:11 These were more noble than those in Thessalonica, in that they received the word with all readiness of mind, and searched the scriptures daily, whether those things were so.
2 Timothy 3:16 All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: 17 That the man of God may be perfect, throughly furnished unto all good works.
If you want to come to grips with what the Bible really teaches, why not take the free Bible study course on www.thisisyourbible.com? You may take this course either online or by regular mail.
This course will give you a background in the major themes of the Bible from Genesis to Revelation. As with everything we offer, there is no cost to you other than your time and effort. You will also have a personal tutor to whom you may pose questions either from the course itself or those questions which come to you as you read the Bible.
I hope you have found this helpful.
May God bless you,