'Remain' in the Bible

What you have heard from the beginning must remain in you. If what you have heard from the beginning remains in you, then you will remain in the Son and in the Father.

The anointing you received from Him remains in you, and you don’t need anyone to teach you. Instead, His anointing teaches you about all things and is true and is not a lie; just as He has taught you, remain in Him.

So now, little children, remain in Him, so that when He appears we may have boldness and not be ashamed before Him at His coming.

This is how we know that we remain in Him and He in us: He has given assurance to us from His Spirit.