1 John 2:24
Abide in Christ.
Don't deny Him.

This verse was written by the apostle John, in the context of a passage that warns about people who can turn you away from your faith. He mentions that, just as there will be a future Anti-Christ, even now already many folks have come who tried to deceive them, who are against Christ. These are people who deny the Father and the Son. 

There are many people who deny that Jesus is the Christ, the promised Messiah whom the Jews were expecting. The Old Testament contains many prophesies about the coming Messiah and they are all fulfilled in Jesus. Our access to God is through Jesus because He bore the penalty for our sins. The only reason He could bear our penalty is because, as God’s Son, He was sinless Himself and so He did not have to die for His own sins. So people that deny the Son-ship of Christ are denying the one true way in which we can get reconciled to God. These are therefore indeed very dangerous false teachers.

The instruction that John gives his readers is to abide in that which they heard from the beginning. What did they hear in the beginning? Probably the good news that Jesus was the promised Messiah and that by believing this good news, they would have eternal life. John 3:16 is a passage that comes to mind, the words that give life. 

John 3:16 For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life. 

What does it mean to have this message abide in you? The Greek word for abide is ‘meno’ and it gets translated as to stay, abide, remain, endure, survive, and continue. So we have to keep this message in us, we should not depart from it. It should live in us, it should grow and bear fruit. 

If that happens, John says that we will then abide in both the Son and the Father. In verse 28, he gives a bit more elaboration of the result of us abiding in God.

1 John 2:28 And now, little children, abide in Him, that when He appears, we may have confidence and not be ashamed before Him at His coming. 

So with your words, with your actions, and with your life, show that you are a Christian. Do not deny Him, never be ashamed of Him, but acknowledge Him as your Savior and as your Lord. Then you will have nothing to be ashamed of at His coming. 

Godspeed!