See, I have told you beforehand.
25. Lo, I have foretold it to you. Mark expresses our Lord’s meaning more fully. But take heed: lo, I have foretold you all things. By these words we are taught that they who are dismayed by the stumbling-blocks which Christ predicted are altogether inexcusable; for since the will of God ought to be our rule, it is sufficient that we have received timely warning that such is his pleasure.
Behold, I have told you before. Meaning not before in this discourse, though he had in Mat 24:5 signified also, that false Christs, and false prophets should arise, but before these things came to pass; so that they had sufficient notice and warning of them, and would be inexcusable if they were not upon their guard against them; and which, when they came to pass...
Verse 25. Behold, etc. Mark adds, "Take ye heed." The reason why he told them before, was that they might be on their guard, and be prepared for those calamities.