Verse 26 All Christians are born again

John 3:3
Jesus answered him, “Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God.”

SIS

John 1:13
who were born, not of blood nor of the will of the flesh nor of the will of man, but of God.

1 Peter 1:23
since you have been born again, not of perishable seed but of imperishable, through the living and abiding word of God;

HIJ

Now for a Gentile when he converted to Judaism, was said to be reborn. You can understand Nicodemus being thrown by this comment.
After it comes on the heels of him praising Him. But Jesus cuts to the chase and wants to impress him of this fact. But Nicodemus confuses it for real birth, not seeing that he as a Jew would need this too, and that it is a spiritual thing. It involves change, from flesh to spirit, and that is independent of us. Like the wind, we cannot control its speed or direction, so we cannot manipulate the work of God, which is the being born again. Like we have no say in our first birth, if He wills us to be His, He will draw us to Himself, by having us view His Son given for us on Calvary.
Galatians 6:14-16
But far be it from me to boast except in the cross of our Lord Jesus Christ, by which the world has been crucified to me, and I to the world. 15 For neither circumcision counts for anything, nor uncircumcision, but a new creation. 16 And as for all who walk by this rule, peace and mercy be upon them, and upon the Israel of God.