What does Matthew 24:23 mean?
Jesus is describing to the disciples a time when great suffering will occur (Matthew 24:21–22). He is describing the times to come after He has left the earth (John 16:5–7) and before His return (Revelation 19:11–15). Here, and in the following verse, He repeats previous warnings about false messiahs (Matthew 24:5) and false prophets (Matthew 24:11, 24).In essence, there are two main points being made. Jesus is assuring the disciples that He is the one and only Messiah, the Christ. Anyone else who makes that claim is absolutely, clearly false. Second, when Jesus returns there will be absolutely zero doubt in anyone's mind what has happened. They won't learn of it by hearing a rumor that the Christ is here or there. Any such gossip or news can be dismissed immediately. The second coming of Christ will be emphatic and unmistakable.
Unfortunately, there will be those who fall for such lies. Jesus goes on to discuss this in the next verses.