Matthew 16:4

You know then how to discern the face of the sky, &c. Jesus Christ does not condemn every observation made upon the weather, from external appearances in the heavens. He only upbraids the Jews for so closely examining these signs, and neglecting at the same time to notice the many signs and predictions which so plainly manifested him to be the promised Messias. (Denis the Carthusian) --- The reasoning of Jesus Christ is this: you know how to judge of the weather from observation, and cannot you then know the certain signs so often promised, and now completed in my coming? The signs of this event were, the taking away the sceptre from the tribe of Juda. (Genesis xxxix. 10.) The completion of the 70 weeks of years of Daniel ix. 25, amounting to 490 years, which were now on the eve of being completed. The miracles of Jesus Christ, as the curing of the blind, the lame, the deaf and dumb, foretold by Isaias xxxv. 5. and lxi. 1. To which may be added the apparition of angels to the shepherds at Bethlehem, the miraculous star which appeared to the magi, the testimony of his heavenly Father, the descent of the Holy Ghost in the form of a dove. Besides, the testimony of the Baptist, and so many miracles of every kind wrought to establish this truth, most certainly, clearly, and infallibly demonstrate, that the long expected Messias had already come, and that this Jesus was the Messias. (Tirinus)