Possible meanings are 1) "If you make a tree good, its fruit will be good, and if you make the tree bad, its fruit will be bad" or 2) "If you consider a tree to be good, it will be because its fruit is good, and if you consider it tree to be bad, it will be because its fruit is bad." This was a proverb. People were to apply its truth to how they can know whether a person is good or bad.
This can be stated in active form. AT: "people know whether a tree is good or bad by looking at its fruit" (See: [[rc://en/ta/man/translate/figs-activepassive]])
"Fruit" is a metaphor for "works" or "actions." AT: "people know whether a tree is good or bad by looking at the results of one's activities." (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "offspring" means "having the characteristic of." Vipers are poisonous snakes that are dangerous and represent evil. See how you translated a similar phrase in [Matthew 3:7](../03/07.md). (See: [[rc://en/ta/man/translate/figs-metaphor]])
Jesus uses a question to rebuke the Pharisees. AT: "you cannot say good things." or "you can only say evil things." (See: [[rc://en/ta/man/translate/figs-rquestion]])
# out of the abundance of the heart his mouth speaks
Here "heart" is a metonym for the thoughts in a person's mind. Here "mouth" is a synecdoche that represents a person as a whole. AT: "what a person says with his mouth reveals what is in his mind" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-synecdoche]])
Jesus speaks about the "heart" as if it were a container that a person fills with good or evil things. This is a metaphor that means what a person says reveals what the person is truly like. If you want to keep this imagery, see the UDB. You can also translate the literal meaning. AT: "A man who is truly good will speak good things, and the man who is truly evil will speak evil things" (See: [[rc://en/ta/man/translate/figs-metaphor]])