I am surprised at some persons view of what born again means or not mean "basic stuff". Some like to explain what born again means here ....clear is good! Are you born again if your NOT indwelt by the Spirit of God?
The New birth, regeneration, quickening are all synonymous terms. They all have to do with new life life, but not physical life - spiritual life. They all presuppose a previous condition of being without spiritual life.
To define new birth is best accomplished by defining its opposite - spiritual death. What is spiritual death?
The Bible clearly says that "death" entered the world by one man's sin (Rom. 5:12a) and death passed upon all men.
So Pentecost is not the start of this problem of death and so Pentecost cannot be the start of the solution of this problem.
However, lets further define exactly what this problem really is.
God told Adam that "in the day" he ate he would die. However, he did not physically die "in the day" he ate as he lived physically to be 930 years of age. He died SPIRITUALLY "in the day" he ate. It is was this instantaneous spiritual death that brought on physical death.
We too, are SPIRITUALLY DEAD and it is that spiritual state of death that brings on our physical death.
What is SPIRITUAL DEATH? Paul defines it as "being alienated from the life of God" - Eph. 4:18. To be alienated is to be separated. God IS LIFE and God IS SPIRIT and to be SPIRITUALLY SEPARATED from the source of life is death.
Hence, the moment Adam sinned he instantaneous was SEPARATED, ALIENATED from God spiritually.
Now, that is the problem that the new birth/quickening/regeneration resolves. It is the opposite of being spiritually SEPARATED from God. What is the opposite of SEPARATION? It is UNION! Our "spirit" is what is born of the Spirit (Jn. 3;6) meaning our spirit is brought back into spiritual UNION with God or the source of life.
Let me illustrate. You have an electric heater disconnected/separated from the wall socket. It is ELECTRICALLY DEAD. However, if you plug the cord of the electric heater into the wall socket it instanteously becomes ELECTRICALLY ALIVE. The difference is between SEPARATION and UNION.
The New birth is being instanteously brought back into spiritual UNION with God who IS LIFE. Hence, spiritual union and new birth are one and the very same thing just as spiritual separation and spiritual death are one and the very same thing.
Now, lets go to the next issue. Where does this spiritual union take place? On mars? In heaven? Outside of your body? No, no, and no. What is born of Spirit is spirit and our spirit INDWELLS our body. For our spirit to be in spiritual UNION with the Spirit of God, the Spirit of God MUST indwell our body as well or there is no spiritual union at all.
That is why Paul defines indwelling of the Spirit as one and the same thing as being "in the Spirit" and if any man have not the Spirit indwelling within him it is because "HE IS NONE OF HIS." The only other possible option is to be "in the flesh" which defines humanity SPIRITUALLY DEAD - Rom. 8:8-9.
So, regeneration by the Spirit IS spiritual union INSIDE you which IS indwelling of the Holy Spirit. One cannot exist apart from the other and without which one IS spiritually dead/separated/alienated from the life of God.
Those who interpret Pentecost wrongly and insist that either regeneration or indwelling did not occur prior to Pentecost are condemning the whole human race prior to Pentecost to spiritual death. They are also demanding THREE different types of human beings; (1) those "in the flesh" versus (2) those "in the Spirit" (3) versus prepentecostal human beings that are neither "in the flesh" or "in the Spirit" according to their interpretation of Pentecost.
God not only IS LIFE but God IS LIGHT. So to be spiritually separated from God not only means one is in a state of SPIRITUAL DEATH or separation from life, but we are also in a state of SPIRITUAL DARKNESS. To be brought back into spiritual union with God is not only to be brought back into spiritual life but spiritual light. Notice, how the unregenerate state is described as the absence of both spiritual light and spiritual life INTERNALLY:
Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart: - Eph. 4:18
So it takes union with both spiritual life and spiritual light to reverse this condition. The reversal of this condition is described as an act of creation by God as in the creation of light in Genesis 1:2-3:
For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ. - 2 Cor. 4:6
Hence, the "light of knowledge" that is necessary to bring a person out of spiritual darkness into spiritual light is not obtained by natural means or by what man can do but it is a creative act of God performed "in the heart." Remember Peter's profession (Mt. 16:16) of faith in Christ? Remember Christ response as to the actual source from which that profession originated?
And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven. - Mt. 16:18
This knowledge that obtains a true profession of faith in Christ comes by a CREATIVE REVELATION from heaven "in the heart." Hence, a saving profession of faith is the work of God (Jn. 6:29) and thus a "gift" of God (Philip. 1:29; Eph. 2:8). It is a CREATIVE act of God (Eph. 2:10). No man is responsible for originating the profession of faith in the heart of man but it is the immediate and direct consequence of a creative act of God in the heart that calls into existence both LIFE and LIGHT due to spiritual union with God. They are no more involved in producing that creative work in their own heart than they were for separating themselves from their mother's womb:
But when it pleased God, who separated me from my mother’s womb, and called me by his grace, To reveal his Son in me, - Gal. 1:15-16a
The "new" birth or "re-generation" is a divine creative act of God and thus a miracle of God just as the physical birth is the work of God and in both cases you are PASSIVE in regard to accomplishing this work "in me" or "in the heart." They do not determine the timing of this work of creation any more than they were active in creating the time of their own separation from their mother's womb. Both births occur "when it pleased God" not when it please you or any other man (Jn. 1:13; James 1:18).