He warns against false christs, and commands vigilance

^21-23 “If anyone tells you at that time, ‘Look, here is Christ’, or ‘Look, there he is’, don’t believe it! For false christs and false prophets will arise and will perform signs and wonders, to deceive, if it be possible, even the men of God’s choice. You must keep your eyes open! I am giving you this warning before it happens.

^24-25 “But when that misery is past, ‘the light of the sun will be darkened and the moon will not give her light; stars will be falling from the sky and the powers of heaven will rock on their foundations’.