Let me step you through a very simple proof that no-one was born again prior to Pentacost.
Jesus is preaching to the Jews:
Joh 8:29 And he that sent me is with me: the Father hath not left me alone; for I do always those things that please him.
As a result of His preaching, many believe!
Joh 8:30 As he spake these words, many believed on him.
By every definition of salvation, if people could be born again, these people must have been. They believed. Jesus continues to speak to these believers:
Joh 8:31 Then said Jesus to those Jews which believed on him, If ye continue in my word, then are ye my disciples indeed;
Joh 8:32 And ye shall know the truth, and the truth shall make you free.
These believers respond to Him:
Joh 8:33 They answered him, We be Abraham's seed, and were never in bondage to any man: how sayest thou, Ye shall be made free?
Jesus responds to these believers:
Joh 8:34 Jesus answered them, Verily, verily, I say unto you, Whosoever committeth sin is the servant of sin.
Joh 8:35 And the servant abideth not in the house for ever: but the Son abideth ever.
Joh 8:36 If the Son therefore shall make you free, ye shall be free indeed.
Joh 8:37 I know that ye are Abraham's seed; but ye seek to kill me, because my word hath no place in you.
Joh 8:38 I speak that which I have seen with my Father: and ye do that which ye have seen with your father.
The believers respond to Him:
Joh 8:39a They answered and said unto him, Abraham is our father.
And agin He responds to these believers:
joh 8:39b
Jesus saith unto them, If ye were Abraham's children, ye would do the works of Abraham.
Joh 8:40 But now ye seek to kill me, a man that hath told you the truth, which I have heard of God: this did not Abraham.
Joh 8:41a Ye do the deeds of your father.
The believers respond to Him:
Joh 8:41b
Then said they to him, We be not born of fornication; we have one Father, even God.
Jesus responds to the believers:
Joh 8:42 Jesus said unto them, If God were your Father, ye would love me: for I proceeded forth and came from God; neither came I of myself, but he sent me.
Joh 8:43 Why do ye not understand my speech? even because ye cannot hear my word.
Jesus calls these believers children of the devil!!!!
Joh 8:44 Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it.
These people were not born again. They still had the unregererate natures within them. They believed.... but the new birth was not yet available to them.