A.T. Robertson Commentary Matthew 12:34

"Ye offspring of vipers, how can ye, being evil, speak good things? for out of the abundance of the heart the mouth speaketh." — Matthew 12:34 (ASV)

Ye offspring of vipers (γεννηματα εχιδνων). These same terrible words the Baptist had used to the Pharisees and Sadducees who came to his baptism (Matthew 3:7). But these Pharisees had deliberately made their choice and had taken Satan's side. The charge against Jesus of being in league with Satan reveals the evil heart within. The heart "spurts out" (εκβαλλε) good or evil according to the supply (treasure, θησαυρου) within. Verse 33 is like Mt 7:17-19. Jesus often repeated his crisp pungent sayings as every teacher does.