Matthew 24:23-31

Then if anyone says to you, ‘Look, here is the Christ!’ or ‘There he is!’ do not believe it. For false christs and false prophets will arise and perform great signs and wonders, so as to lead astray, if possible, even the elect. See, I have told you beforehand. So, if they say to you, ‘Look, he is in the wilderness,’ do not go out. If they say, ‘Look, he is in the inner rooms,’ do not believe it. For as the lightning comes from the east and shines as far as the west, so will be the coming of the Son of Man. Wherever the corpse is, there the vultures will gather. “Immediately after the tribulation of those days the sun will be darkened, and the moon will not give its light, and the stars will fall from heaven, and the powers of the heavens will be shaken. Then will appear in heaven the sign of the Son of Man, and then all the tribes of the earth will mourn, and they will see the Son of Man coming on the clouds of heaven with power and great glory. And he will send out his angels with a loud trumpet call, and they will gather his elect from the four winds, from one end of heaven to the other.

signs and wonders - See Revelation 13.

if possible, even the elect - but it isn’t, either because of God’s protection or because the days are shortened, or both

I have told you beforehand - See Matthew 7:15; 15:3-14; 16:6-12; 23:1-36; 24:11.

"This is a warning as well as a prediction." (Ryrie)

"If told that Messiah has come already and is manifesting Himself in the desert they are not to go forth seeking Him there. If told He is hidden in some secret place they are not to believe it. For His coming will be in visible manifested glory when He shines forth from heaven as lightning flaming athwart the sky." (Ironside)

Verse 28 is saying that, as where there is death, there will be vultures, so where there is corruption, there will be judgment.

those days - See Revelation 6:12-14.

the sun...the moon...the stars - "These astral phenomena, which will accompany the return of the Son of Man, are foretold in Isa 13:9-10 and Joel 2:31; 3:15." (Ryrie)

the sign - probably the Shekinah cloud (Acts 1:9-11)

"Some think this is the lightning of verse 27, others the Shekinah, or glory, of Christ; still others leave it unspecified.  At any rate, the Son of Man Himself will come visibly (Rev 1:7).  There seems to be no reason for not taking this part of Jesus' teaching as plainly as other parts." (Ryrie)

tribes of the earth = lit. "of the land" - Israel! - Zechariah 12:10-12

mourn - an intense, ritualistic mourning

they will see the Son of Man - Revelation 1:7: "Behold, He is coming with clouds, and every eye will see Him, even they who pierced Him. And all the tribes of the earth will mourn because of Him. Even so, Amen."

trumpet call - the gathering of Israel - Isaiah 11:11-12; Isaiah 27:13

"Christ now proceeded to describe the third eschatological event in Israel’s program — the restoration of the nation Israel back to the land. Since this whole discourse has been devoted to the prophetic program for Israel, the reference to 'His elect' (Matthew 24:31) cannot refer to the church. Instead, the reference must be to the nation that God had chosen (Exodus 19:5-6). During the Tribulation Israel will be scattered out of the land by military invasions. The Israelites will flee and find refuge among the Gentile nations. God will supernaturally bring the people of Israel back to the land through the instrumentality of angels. This will be the final restoration anticipated in the Old Testament (Deuteronomy 30:1-8)." (Pentecost)