en_tn_lite_do_not_use/ecc/10/20.md

not even in your mind

AT: "not even in your thoughts" (See: rc://en/ta/man/translate/figs-metonymy)

the rich in your bedroom

"the rich when you are in your bedroom." This means that you should not curse rich people even when you are in a private place where no one else will hear.

For a bird of the sky. . .can spread the matter

These two lines mean basically the same thing and are combined for emphasis. The writer uses the metaphor of a bird to say that people will find out what you have said, one way or another. (See: rc://en/ta/man/translate/figs-parallelism and rc://en/ta/man/translate/figs-metaphor)