What does 勿恃富而欺窮 (물시부이기궁) mean?

I am rewriting an old textbook on Literary Chinese so that it can be used by English-speaking Koreans or by English-speaking Korean language learners. The project is taking longer than I expected because I am having to retranslate a lot of the original translations. Today, for example, I came across the following Chinese sentence and translation:

勿(물)恃(시)富(부)而(이)欺(기)窮(궁).

“Do not rely on wealth and ill-treat the poor.”

The translation makes sense, but one should suspect it is missing something because the ancient Chinese philosophers and scholars were some of the most clever men in history. A lot of thought went into their sentences. They could squeeze a whole paragraph into a cleverly constructed, 4-character sentence, therefore, when I see a translation that does not have, at least, a double meaning, I get suspicious and start looking for the hidden meanings or clever wording.
Therefore, I would also like to suggest the following translation:

"Do not (勿) trust (恃) the rich (富) if (而) [you] cheat (欺) the poor (窮)."

In other words, if you are willing to cheat the poor, you should assume the rich are willing to cheat you since they may see you as poor. The character 而 (이) can also mean "and," "but," or "while," so here are a couple more possible translations.

"Do not (勿) trust (恃) the rich (富) and (而) cheat (欺) the poor (窮)."

"Do not (勿) trust (恃) the rich (富) while (而) cheating (欺) the poor (窮)." 

The character 恃 (시) can mean "to rely on" or "to depend on," but it can also mean "to believe" or "to trust."