«رَاكِبْ بَلَاشْ وِيْنَاغِشْ مِرَاتِ الرَّيِّسْ»

The saying sketches a passenger whom a boat's skipper has allowed aboard without charge, and who answers that kindness by flirting with the skipper's wife. The picture is of the worst kind of return for a favor: the beneficiary turns against the very household that sheltered him.

Applied to people, it brands someone as contemptible for answering generosity with betrayal or disgrace. The force lies in the contrast: the greater the kindness received, the more shameful the injury done in return, and the more clearly it exposes a base, ungrateful character.

Use it to condemn someone who repays a favor with an offense, especially one who exploits a host's generosity or trust. It suits scornful remarks about ingratitude and carries a judgment of the person's character, so it is insulting when aimed directly at someone.