your question is not grammatically structured properly. a Christian can not become born again because a Christian IS ALREADY born again. 1st, you become born again, then you are a Christian.. when someone says "the sinners prayer" & truly believes in God, Jesus & the Holy Spirit, then you become Christian at that moment.
The word warns about following manmade traditions. because they have the ability to make God's word of none effect. (Matt. 15:6) In other words they steer people away from God and His lifegiving message. The "sinner's prayer" is not in the bible it is a manmade tradition.
Paul stated having the Holy Spirit is essential to be accepted of God. (Rom. 8:9) Believing does not automatically bring about that reality. We know this from Paul's question recorded in Acts 19, "Have you received the Holy Ghost
SINCE you believed?" The question shatters the illusion that belief alone provides for the indwelling of the Holy Ghost/Spirit. Further, the question indicates Paul was going to assist the group in receiving the Holy Ghost if they hadn't already had the experience. Please read the entire account in Acts 19:1-6 it provides the answer to how a person becomes born again via water and Spirit. Note: The detailed account mirrors the instructions given by Peter over 25 years earlier when the NT church was birthed.
Peter provided instructions when asked "What must we do?" by those on the Day of Pentecost. It is noted in the last verse when the group was considered born again Christians:
"Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ.
Now when they heard this, they were pricked in their heart,
(THEY BELIEVED) and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?
(WHAT ELSE IS NECESSARY)
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.
For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.
And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation.
Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls." (Acts 2:36-41)