Question:
What is the difference between the Holy Spirit and the new nature?

Answer:

He gives us a whole new nature, not just fixing the old one, and He gave us the Holy Spirit. The Holy Spirit is the third Person of the Godhead whom Christ sent to indwell believers the moment they are saved.

Jesus said: “I will pray the Father, and He shall give you another Comforter, that He may abide with you for ever; even the Spirit of truth; whom the world cannot receive, because it seeth Him not, neither knoweth him: but ye know Him; for He dwelleth with you, and shall be in you” (John 14:16, 17).

“In whom [Christ] ye also have trusted, having heard the word of the truth, the glad tidings of your salvation; in whom also, having believed, ye have been sealed with the Holy Spirit of promise, who is the earnest of our inheritance to the redemption of the acquired possession to the praise of his glory” (Ephesians 1:13, 14; JND translation).