The Gospel is 'Salvation comes through faithing in Christ'. The Holy Spirit in the human spirit is the Gospel of Good news, because you cannot of your efforts exhibit the character of God in your human behavior and life. ONLY by His indwelling spirit is the character of God displayed in the life of a human being.
Ephesians 4:6 One God and Father of all, who is above all, and through all, and in you all.Philippians 2:13 For it is God which worketh in you both to will and to do of his good pleasure.
Colossians 1:27 To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:
1 Peter 3:15 But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear:
The following passages should all be read as a continuous assurance:
Luke 15:10 Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth.
Luke 7:28 For I say unto you, Among those that are born of women there is not a greater prophet than John the Baptist: but he that is least in the kingdom of God is greater than he.
Luke 18:17 Verily I say unto you, Whosoever shall not receive the kingdom of God as a little child shall in no wise enter therein. [An interesting thing about little children, that they believe and accept so innocently. Thereby the Promises made to them they accept as absolutely guaranteed.]
Romans 8:9 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.
Romans 15:13 Now the God of hope fill you with all joy and peace in believing, that ye may abound in hope, through the power of the Holy Ghost.
1 Corinthians 3:16 Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?
1 Corinthians 6:11 And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
1 Corinthians 6:19 What? know ye not that your body is the temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own?
1 Thessalonians 2:13 For this cause also thank we God without ceasing, because, when ye received the word of God which ye heard of us, ye received it not as the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe.
1 John 4:4 Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world.