7. But when he saw many of the Pharisees and Sadducees come to his baptism, he said unto them--astonished at such a spectacle.
      O generation of vipers--"Viper brood," expressing the deadly influence of both sects alike upon the community. Mutually and entirely antagonistic as were their religious principles and spirit, the stern prophet charges both alike with being the poisoners of the nation's religious principles. In Mt 12:34; 23:33, this strong language of the Baptist is anew applied by the faithful and true Witness to the Pharisees specifically--the only party that had zeal enough actively to diffuse this poison.
      who hath warned you--given you the hint, as the idea is.
      to flee from the wrath to come?--"What can have brought you hither?" John more than suspected it was not so much their own spiritual anxieties as the popularity of his movement that had drawn them thither. What an expression is this, "The wrath to come!" God's "wrath," in Scripture, is His righteous displeasure against sin, and consequently against all in whose skirts sin is found, arising out of the essential and eternal opposition of His nature to all moral evil. This is called "the coming wrath," not as being wholly future--for as a merited sentence it lies on the sinner already, and its effects, both inward and outward, are to some extent experienced even now--but because the impenitent sinner will not, until "the judgment of the great day," be concluded under it, will not have sentence publicly and irrevocably passed upon him, will not have it discharged upon him and experience its effects without mixture and without hope. In this view of it, it is a wrath wholly to come, as is implied in the noticeably different form of the expression employed by the apostle in 1Th 1:10. Not that even true penitents came to John's baptism with all these views of "the wrath to come." But what he says is that this was the real import of the step itself. In this view of it, how striking is the word he employs to express that step--fleeing from it--as of one who, beholding a tide of fiery wrath rolling rapidly towards him, sees in instant flight his only escape!

JFB.