But take ye heed,.... The Persic version adds, "of them"; of the false Christs, and false prophets: for though the purposes of God, concerning the salvation of his elect, are infrustrable; his promises are yea and amen; his grace is efficacious and irresistible, and his power uncontrollable; and the salvation of his chosen ones certain; yet it becomes them to be on their guard against every deception, and temptation, and to make use of all means for their perseverance:
behold, I have foretold you all things; relating to the destruction of the temple, city, and nation of the Jews; the signs that would go before it, as the disciples had desired; the miseries and calamities that would attend it, and the danger they would be exposed to through false Christs, and false prophets; and therefore would be inexcusable, if they did not observe the caution he now gave them: and moreover, when all these should be accomplished, they would remember that he had told them of them beforehand; which would be a proof of his omniscience, and so an establishment of them in the truth of him, as the Messiah; See Gill on Matthew 24:25.

But take ye heed; behold, I have foretold you all things--He had just told them that the seduction of the elect would prove impossible; but since this would be all but accomplished, He bids them be on their guard, as the proper means of averting that catastrophe. In Matthew (Matthew 24:26-28) we have some additional particulars: "Wherefore, if they shall say unto you, Behold, He is in the desert; go not forth: behold, He is in the secret chambers; believe it not. For as the lightning cometh out of the east, and shineth even unto the west; so shall also the coming of the Son of man be." See on Luke 17:23-24. "For wheresoever the carcass is, there will the eagles be gathered together." See on Luke 17:37.