The Holy Spirit
The Holy Spirit convicts sinners of their need of forgiveness. He regenerates, indwells, baptizes and seals all those who are true believers in Christ, helping them to live a life that is pleasing to God. The Holy Spirit also takes the things of Christ and reveals them, enriching the soul of individual believers and helping to develop Christ-like character.
This is what the Bible says about the Holy Spirit -
“And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: of sin, because they believe not on me; of righteousness, because I go to my Father, and ye see me no more; of judgment, because the prince of this world is judged ... when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come. He shall glorify me: for he shall receive of mine, and shall shew it unto you. All things that the Father hath are mine: therefore said I, that he shall take of mine, and shall shew it unto you.” John 16: 6-15
“But ye are not in the flesh, but in the Spirit, if so be that the Spirit of God dwell in you. Now if any man have not the Spirit of Christ, he is none of his. And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness. But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you.
Therefore, brethren, we are debtors, not to the flesh, to live after the flesh. For if ye live after the flesh, ye shall die: but if ye through the Spirit do mortify the deeds of the body, ye shall live. For as many as are led by the Spirit of God, they are the sons of God. For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father. The Spirit itself beareth witness with our spirit, that we are the children of God” Romans 8: 9-16
“ ... In Christ. 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 that holy Spirit of promise, which is the earnest of our inheritance ...” Ephesians 1: 13-14