That has nothing to do with members of the Body of Christ. We are sealed unto the day of redemption (Ephesians 1:13-14 KJV, Ephesians 4:30 KJV).
I thought you said you believed what Paul says?
1 Corinthians 15:2 By this gospel you are saved, if you hold firmly to the word I preached to you. Otherwise, you have believed in vain.
Galatians 3:4 Have you experienced so much in vain--if it really was in vain?
Do you know what believing in vain means?
1 Corinthians 10:12 So, if you think you are standing firm, be careful that you don't fall!
Why is Paul warning us not to fall?
Romans 11:22 Consider therefore the kindness and sternness of God: sternness to those who fell, but kindness to you, provided that you continue in his kindness. Otherwise, you also will be cut off.
Here Paul says they can be cut off as the unbelieving Jews were cut off.
Romans 2:3 So when you, a mere human being, pass judgment on them and yet do the same things, do you think you will escape God’s judgment?
1 Corinthians 11:31 But if we were more discerning with regard to ourselves, we would not come under such judgment.
1 Timothy 3:6 He must not be a recent convert, or he may become conceited and fall under the same judgment as the devil.
What happened to the recent convert? And why does Paul warn about coming under judgement?