Yes, with a brother in Christ, that I may better serve the Lord.
Here is a passage where believers are councelled to test the spirits, to determine whether of God, or a spirit of antichrist. This can be used to determine who is a Christian.
I talk about this passage in my recording below.
Edit [Moderator]: Link removed
Holy Bible - 1 John 4:1-3 King James Version (KJV)
1 Beloved, believe not every spirit, but try the spirits whether they are of God: because many false prophets are gone out into the world.
2 Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God:
3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world.