Those who are born again can be sure. Jesus made it clear in his discussion with Nicodemus, found in the third chapter of John's Gospel. Believing on the Son of God was the real issue. Those who are born again believe on the Lord Jesus Christ (John 3:16, 36). That is how new birth is sure, based upon the clear teaching of the Bible.
Our first birth was by the flesh. Our new birth is by the Spirit. Our new birth is the work of the Holy Spirit, through faith in Jesus Christ our Lord. Those who are born again can be sure, because they believe on the Lord Jesus Christ. "Whoever believes that Jesus is the Christ is born of God" (1 John 5:1).
Jesus said to Nicodemus, "If I told you earthly things and you do not believe, how will you believe if I tell you heavenly things?" (John 3:12). Nicodemus was a religious man who was not born again. His unbelief was the evidence. Only God knows how many religious people today are not born again.
Believing on the Lord Jesus Christ means your new birth is sure (Acts 16:31). All who are born again believe the gospel of Jesus Christ (Romans 1:16). We believe Christ died for our sins, according to the Scripture. We believe Christ is risen from the dead, according to the Scripture (1 Corinthians 15:1-4). That's how our new birth is sure.
