Even in I John
I John 2:22 - Who is a liar but he that denieth that Jesus is the Christ? He is antichrist, that denieth the Father and the Son.
I John 5:1 -  Whosoever believeth that Jesus is the Christ is born of God: and every one that loveth him that begat loveth him also that is begotten of him.

Acts 13:8: But Elymas the sorcerer (for so is his name by interpretation) withstood them, seeking to turn away the deputy from the faith.

Acts 14:22: Confirming the souls of the disciples, and exhorting them to continue in the faith, and that we must through much tribulation enter into the kingdom of God.

Acts 16:5: And so were the churches established in the faith, and increased in number daily.

Romans 1:5: By whom we have received grace and apostleship, for obedience to the faith among all nations, for his name:

Romans 14:1: Him that is weak in the faith receive ye, but not to doubtful disputations.

I Corinthians 16:13: Watch ye, stand fast in the faith, quit you like men, be strong.

Galatians 1:23: But they had heard only, That he which persecuted us in times past now preacheth the faith which once he destroyed.

*Galatians 2:16: Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.

Also see Romans 3:22 - Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:

*Galatians 2:20: I am crucified with Christ: nevertheless I live; yet not I, but Christ liveth in me: and the life which I now live in the flesh I live by the faith of the Son of God, who loved me, and gave himself for me.

*Ephesians 3:12: In whom we have boldness and access with confidence by the faith of him.

Ephesians 4:13: Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:

*Philippians 3:9: And be found in him, not having mine own righteousness, which is of the law, but that which is through the faith of Christ, the righteousness which is of God by faith:

Colossians 2:7: Rooted and built up in him, and stablished in the faith, as ye have been taught, abounding therein with thanksgiving.

*I Timothy 3:13: For they that have used the office of a deacon well purchase to themselves a good degree, and great boldness in the faith which is in Christ Jesus.

II Timothy 4:7: I have fought a good fight, I have finished my course, I have kept the faith:

Titus 1:13: This witness is true. Wherefore rebuke them sharply, that they may be sound in the faith;

Titus 3:15: All that are with me salute thee. Greet them that love us in the faith. Grace be with you all. Amen.

Tribulation
James 2:1: My brethren, have not the faith of our Lord Jesus Christ, the Lord of glory, with respect of persons.

I Peter 5:9: Whom resist stedfast in the faith, knowing that the same afflictions are accomplished in your brethren that are in the world.

Jude 1:3: Beloved, when I gave all diligence to write unto you of the common salvation, it was needful for me to write unto you, and exhort you that ye should earnestly contend for the faith which was once delivered unto the saints.

Revelation 13:10: He that leadeth into captivity shall go into captivity: he that killeth with the sword must be killed with the sword. Here is the patience and the faith of the saints.

Revelation 14:12: Here is the patience of the saints: here are they that keep the commandments of God, and the faith of Jesus.

Still always remember:  II Timothy 2:13:  If we believe not, yet he abideth faithful: he cannot deny himself.
You still can not 'lose' your salvation - you can 'quit' but He won't quit on you!

But folks can still 'choose' to:
These last 6 verses sure seem to be the way it is today, eh!

Depart from the faith!
I Timothy 4:1: Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;

Deny the faith!
I Timothy 5:8: But if any provide not for his own, and specially for those of his own house, he hath denied the faith, and is worse than an infidel.

Err from the faith!
I Timothy 6:10: For the love of money is the root of all evil: which while some coveted after, they have erred from the faith, and pierced themselves through with many sorrows.

Err concerning the faith!
I Timothy 6:21: Which some professing have erred concerning the faith. Grace be with thee. Amen.

Overthrow the faith - or allow yours to be overthrown!
II Timothy 2:18: Who concerning the truth have erred, saying that the resurrection is past already; and overthrow the faith of some.

Be reprobate concerning the faith!
II Timothy 3:8: Now as Jannes and Jambres withstood Moses, so do these also resist the truth: men of corrupt minds, reprobate concerning the faith.
reprobate - abandoned to error, or in apostasy.

Get away from it all by quit listening, reading, etc. and not listening to Paul's gospel /epistles.
Colossians 1:23: If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister;