The basic thesis for this post is easily stated: In the gospels and Acts salvation is equated with receiving the Holy Spirit.
That might seem to be an obvious point, but let it sink in. Salvation in the gospels and Acts isn't associated with the atonement. Salvation is associated with being given the Holy Spirit.
In the gospels this association is most clearly seen in John:
John 3.5-8Being saved is being "born again" in a mystical, spiritual, metaphysical sense. Simply: "That which is born of the Spirit is spirit." In John 6.63 Jesus says, "It is the Spirit that gives life."
Jesus answered [Nicodemus], “Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the kingdom of God. That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. Do not marvel that I said to you, ‘You must be born again.’ The wind blows where it wishes, and you hear its sound, but you do not know where it comes from or where it goes. So it is with everyone who is born of the Spirit.”
Salvation is life, and the Spirit is what gives us life.
The Synoptic gospels are less mystical when it comes to the Spirit, but they agree with John that the coming of the kingdom is associated with the advance of the Spirit.
John the Baptist declares, “I have baptized you with water, but he will baptize you with the Holy Spirit."
Jesus' ministry of exorcism is viewed in the Synoptics as the Holy Spirit reclaiming enemy-held territory:
Matthew 12.22-28In Acts 1 and 2 the church--the community of the saved--is established at Pentecost by the pouring out of the Holy Spirit. In Acts 10 the mission to the Gentiles is inaugurated when the Holy Spirit falls upon Cornelius and his household.
Then a demon-oppressed man who was blind and mute was brought to him, and he healed him, so that the man spoke and saw.
And all the people were amazed, and said, “Can this be the Son of David?” But when the Pharisees heard it, they said, “It is only by Beelzebul, the prince of demons, that this man casts out demons.”
Knowing their thoughts, he said to them, “Every kingdom divided against itself is laid waste, and no city or house divided against itself will stand. And if Satan casts out Satan, he is divided against himself. How then will his kingdom stand? And if I cast out demons by Beelzebul, by whom do your sons cast them out? Therefore they will be your judges. But if it is by the Spirit of God that I cast out demons, then the kingdom of God has come upon you."
In fact, the entire book of Acts is simply the story of how the Spirit that filled Jesus now fills and guides the church. The Spirit is the hero of the book of Acts. How a person stands in relation to the Spirit in the book of Acts tells us how they stand in relation to salvation, the church, and the advancing kingdom of God.
So the main point: in the gospels and the book of Acts salvation is described as receiving the Holy Spirit.