Charles Spurgeon Commentary 1 John 5:18-21

"We know that whosoever is begotten of God sinneth not; but he that was begotten of God keepeth himself, and the evil one toucheth him not. We know that we are of God, and the whole world lieth in the evil one. And we know that the Son of God is come, and hath given us an understanding, that we know him that is true, and we are in him that is true, [even] in his Son Jesus Christ. This is the true God, and eternal life. [My] little children, guard yourselves from idols." — 1 John 5:18-21 (ASV)

But he that is begotten of God keeps himself, and that wicked one touches him not. And we knew that we are of God, and the whole world lies in wickedness. And we know that the Son of God has come, and has given us an understanding, that we may know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life. Little children, keep yourselves from idols.

At the time of the Reformation, there was a general order that this text should be put around the communion tables. I think it is time that it was put around the communion tables again. Little children, keep yourselves from idols;—for that is one place where idols are often found, though not by any means the only one.