From the beginning of time on this earth, the spirit has been connected with life. It was the Spirit of God breathed into man bringing him to life (Genesis 2:7). Jesus tells us plainly that it is the Spirit who gives life (John 6:63), and James further states that "the body without the spirit is dead." (James 2:26) If it is the Spirit that gives us life and keeps us alive, what is the significance of Peter's promise to those who would repent and be baptized in Acts 2:38, that they might receive the gift of the Holy Spirit? The Spirit already gives and sustains us physically (Job 33:4). Thus, there must be more than just physical blessings that God, through the mouth of Peter, was promising.
John the Baptist, in Matthew 3:11, mentions that Christ would baptize with the Holy Spirit and fire. Christ then explains this more clearly in Acts 1:8,
But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judea, and in Samaria, and unto the uttermost part of the earth.
Acts 2:3-4, the fulfillment of Christ's statement, says,
And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
Much like baptism into the watery grave completely covers us, so too did the Holy Spirit when it descended upon each of the apostles, baptizing them with the Spirit and fire as John had prophesied. However, Peter does not tell us, in Acts 2:38, that this "gift of the Holy Spirit" would be anything similar to what the "men and brethren" (v. 37) had just witnessed. In fact, we only see one other time where the Spirit, without the laying on of the Apostles hands, descended upon a group of People. In Acts 10:44 the Holy Spirit falls upon the household of Cornelius, a gentile. The passage makes clear:
that he and his household were not immersed into water till after this baptism by the Holy Spirit
that it was a sign to show God's acceptance of the Gentiles into His kingdom (Acts 11:15-17)
Therefore, it is also clear that Peter was not promising that we would receive the baptism of the Holy Spirit, whereby we would begin speaking in tongues, as Cornelius and the Apostles did. What, then, has God promised us through Peter?
In Romans 8:10 we find,
And if Christ is in you, the body is dead because of sin, but the Spirit is life because of righteousness.
Galatians 6:8 further explains this life,
For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting.
When we give our life to Christ, and submit to Him through the act of baptism, we put to death the flesh and all its carnal natures, allowing the Spirit of God to dwell in us, giving us newness of life and the hope of eternal life. Romans 8:13 says,
For if you live according to the flesh, you will die; but if by the Spirit you put to death the deeds of the body, you will live.
God is telling us, if we will follow Him, He will give us life everlasting, and to testify of His promise, His Spirit will dwell in us from the moment we arise from being immersed. Therefore Paul says in I Corinthians 6:19,
What? Know ye not that your body is the Temple of the Holy Ghost which is in you...
The Spirit of God dwells in us. We are not our own to do whatsoever we please, but rather God's to follow wheresoever His Spirit guides us.
How then does this gift of the Holy Spirit dwelling in us give us life? We know that it does, but how?
Back in Exodus 12 the children of Israel were told to mark their doors with the blood of a lamb, and that this blood would be a sign to God, setting those who were His apart from the Egyptians. Through this sign, the firstborn sons of all Israel receive life. So too, in Ezekiel 9, the man clothed in linen wearing an inkhorn on his side (v. 3) is told to mark the "foreheads of the men who sigh and cry for all the abominations..." (v. 4) done in Jerusalem. When God, through the Babylonians, destroyed Jerusalem, these men with the mark on their foreheads would be preserved. That mark sealed them in the day of judgment, preserving their life.
Ephesians 1:13 In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation; in whom also after that ye believed, ye were sealed with the Holy Spirit of promise.
By seal, here, Paul is indicating that the Holy Spirit, as is given to us through the promise in Acts 2:38, stamps us as God's people. Like the man with the inkhorn or the blood on the door, so God, as a king would a document, seals us, and attests to our preservation through His Spirit.
II Thessalonians 2:13 makes this even clearer:
But we are bound to give thanks alway to God for you, brethren, beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief in the truth.
Therefore, the Holy Spirit gives us life by sealing us as one of God's own children (Romans 8:15). He seals us because His presence in us sanctifies us, and sets us apart. So then, though the world may think it strange, we are not to run with them in the same riotous living (I Peter 4:4), but rather we are to walk as His "own special people..." (I Peter 2:9) sealed by the Spirit for redemption.
Romans 14:17 for the kingdom of God is not eating and drinking, but righteousness and peace and joy in the Holy Spirit.
This gift from God is truly magnificent. Who of us is worthy of God's Spirit dwelling in us? God wants us to know just how much He loves us (Romans 5:5), and so He gives His Spirit to preserve us (Titus 3:5), to assure us (I John 3:24), and to assist us each and everyday of our walk with God (Romans 8:14).
Therefore, Ephesians 4:30 states,
And grieve not the Holy Spirit of God, whereby ye are sealed unto the day of redemption.