Translation
Even in your thoughts, do not curse the king and even in your bed-chamber do not curse the rich, for a bird of the air may carry away your voice, and a possessor of wings
Go to footnote numbermay make the matter known.
Paraphrase
Do not curse an authority figure, even if you think no one can hear you, and do not curse those who have money and connections, even in your most private place, because the ruler may hear about it in unexpected ways, and the powerful might hear about it in ways you would never imagine.
Footnotes
1: “possessor of wings”
This is the same construction as “the owner of the tongue” in verse 11 of this chapter. It is a reference to any flying creature. The term literally means “master of wings;” a master of something owns it, so this is a creature that possesses wings, hence a flying creature of any kind. Since birds cannot talk and communicate a message it seems like an impossible scenario; likewise, when you think it would be impossible for those in authority to hear about something you do or say, be careful, because you may find out that the impossible is indeed possible.