(34) O generation of vipers.--Better, as in Matthew 3:7, brood of vipers. Here the law which had been pressed in its logical bearing in the preceding verse, is brought in to explain the bitter and evil words of the Pharisees. As long as they were what they were, nothing else was to be looked for. Nothing but the serpent's hiss could come from the brood of vipers, nothing but bitter words from hearts so full of bitterness.

Verse 34. - The first clause is in Matthew only. O generation (ye offspring, Revised Version) of vipers (Matthew 3:7, note). Observe that the figure of the tree had also been used by the Baptist (Matthew 3:10). How can ye. It is against nature. Being evil; i.e. inherently worthless (Matthew 6:13, note); cf. πονηροὶ ὄντες, Matthew 7:11. Speak good things. For out of the abundance; i.e. even to overflowing (περίσσευμα: cf. Mark 8:8, of what remained after all were filled). Of the heart the mouth speaketh. In Ephesians 4:29 there is apparently a reminiscence of this saying in connexion with our ver. 33 (cf. also James 3:10-12).

12:33-37 Men's language discovers what country they are of, likewise what manner of spirit they are of. The heart is the fountain, words are the streams. A troubled fountain, and a corrupt spring, must send forth muddy and unpleasant streams. Nothing but the salt of grace, cast into the spring, will heal the waters, season the speech, and purify the corrupt communication. An evil man has an evil treasure in his heart, and out of it brings forth evil things. Lusts and corruptions, dwelling and reigning in the heart, are an evil treasure, out of which the sinner brings forth bad words and actions, to dishonour God, and hurt others. Let us keep constant watch over ourselves, that we may speak words agreeable to the Christian character.O generation of vipers,.... Though they boasted of their being the seed of Abraham, yet their immediate ancestors were no other than vipers, deceitful, hurtful, poisonous creatures; and they were exactly like them: for though they made a fair show in the flesh, and outwardly appeared righteous, yet were inwardly full of the poison of wickedness, envy and malice; and which their pestilential breath, their blasphemy against the Spirit, fully discovered; and gave just cause and reason for so severe a reproof, and such resentment, as here made by Christ.

How can ye, being evil, speak good things? This is not to be expected, nor is it commonly and constantly done; an evil man may sometimes speak good things, or which seem to be so; but these are not his common talk; as he is, so, for the most part, is his language; his speech betrays him: and since these men were by nature evil, were destitute of the Spirit and grace of God, had no good thing in them, how should any good thing come out of them? And since they were so full of wickedness, spite and malice, it is no wonder that they belched out such blasphemous expressions concerning the miracles of Christ;

for out of the abundance of the heart the mouth speaketh: a phrase much like this is used by the Septuagint, in Ecclesiastes 2:15. "I spoke abundance", or "much in my heart"; "for the fool out of his abundance speaketh": as there is abundance of folly in him, there is much delivered out by him; and where there is abundance of wickedness in the heart, if the grace of God is wanting to restrain it, much of it will come out by the lips; as is a man's heart, ordinarily is his language.