Ver. 34,35. The evangelist Luke, Luk_6:45, hath much the same with what is here.
O generation of vipers: John had so called them, and Christ again so called them, Mat_23:33. A viper is of all other the most venomous and dangerous serpent. Christ is calling them a generation of vipers, intimates that the Pharisees were generally a most mischievous faction for the souls of men.
How can ye, being evil, speak good things? Why do I (saith he) spend my time and breath in reproving or admonishing you? you have cankered hearts, full of pride, malice, and envy, and therefore, cannot ordinarily speak good things.
For out of the abundance of the heart the mouth speaketh: what men ordinarily and deliberately do speak is from the affections and thoughts of their hearts. Hence good men out of the good treasure of their hearts speak good things, that is, most ordinarily and commonly; and evil men out of the stock of malice, revenge, envy, pride and other lusts, which are in their hearts, speak evil things.