2 Corinthians 13:5: Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?
Romans 8:16: The Spirit itself beareth witness with our spirit, that we are the children of God:
If you depend upon anyone other than yourself and the Lord to convince you that you are a Christian you are shirking a personal responsibility that is given to all of us by God to examine ourselves. Only the Lord can look upon our hearts.
1 Samuel 16:7: But the LORD said unto Samuel, Look not on his countenance, or on the height of his stature; because I have refused him: for the LORD seeth not as man seeth; for man looketh on the outward appearance, but the LORD looketh on the heart.
The phrase in the faith makes it obvious that the faith is something bigger than us. It is also obvious that some people are not in it.
2 Timothy 1:5: When I call to remembrance the unfeigned faith that is in thee, which dwelt first in thy grandmother Lois, and thy mother Eunice; and I am persuaded that in thee also.
Not only are we to be in the faith but it must also be in us. It is something that you get into and when you get into it, it gets into you.
A poor illustration would be that of a sponge submerged in water. Not only is the sponge in the water but the water gets into the sponge. A sponge is changed by being in water and by having water in it. Just as a sponge is changed by being in water and having water in it we cannot fail to be changed by being in the faith and having the faith in us.
Being in the faith is necessarily a personal thing. A sponge cannot be in water on behalf of another sponge. Neither can a person can be in the faith on behalf of another person. A sponge cannot change itself and neither can we. The sponge must be changed by the water and we must be changed by the Lord Himself.
Psalms 25:14: The secret of the LORD is with them that fear him; and he will shew them his covenant.
In every one-on-one relationship there are secret things that no one else knows about. If there are not things that you share with God alone you don*t have a one-on-one relationship with Him; you are not in Him and He is not in you. Jacob and Moses met with God face to face. We don*t just meet God face to face. We meet Him heart to heart.
Genesis 32:30: And Jacob called the name of the place Peniel: for I have seen God face to face, and my life is preserved.
Exodus 33:11a: And the LORD spake unto Moses face to face, as a man speaketh unto his friend. . . .
Thomas used the personal possessive word *my* when he saw and spoke to the resurrected Lord Jesus.
John 20:28: And Thomas answered and said unto him, My Lord and my God.