V.15-17 “The world” is referring to the spirit of the world, not this physical world. In this Epistle, John is writing to us believers as being in the family of God. Every believer in Christ is in it. How we behave is what these words are about.
V.18-19 We are hearing more and more about people who claim to be “the Christ.” Keep as far away as possible from them. We know that it is the “last time.”
V.20 Every believer who listens to the Word of God and bows to it hears exactly the same as every other who does likewise. This is what brings unity among the Lord’s people.
V.22-23 Two comforting views of the Lord Jesus — as the Christ and as the Son of God. When people deny this, they lie. It is very important to believe this.
V.28 As you read through this Epistle, you can see that almost everything mentioned is built upon what the Lord Jesus said on His last night on earth; John 13-16. Read this verse and then read John 14:3. This promise banishes all anxiety and disturbance in our life.