Matthew 12:34
You offspring of vipers, how can you, being evil, speak good things? For out of the abundance of the heart, the mouth speaks.
World English Bible (Public Domain)
In context
Before · Matthew 12:32–33
32Whoever speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age, or in that which is to come. 33“Either make the tree good and its fruit good, or make the tree corrupt and its fruit corrupt; for the tree is known by its fruit.
34You offspring of vipers, how can you, being evil, speak good things? For out of the abundance of the heart, the mouth speaks.