But: the conjunction here should show the contrast between what might happen if Hushai stayed with David and what might happen if he returned to Jerusalem. Good News Translation adds “you can help me” to highlight the opposite of being a hindrance, which was mentioned in the previous verse.
It should be clear to readers that the city refers to Jerusalem.
If the quote within another quotation will be very difficult to render, it will be better to make one or both of the quotations indirect. Good News Translation has made the part about what Hushai is to say to Absalom indirect.
Your father’s servant: some may need to say more clearly “the servant of your father, David.”
Defeat for me the counsel of Ahithophel: in place of the verb defeat or “oppose” (Good News Translation), it may be better to use a verb like “spoil” or “ruin.” As the context indicates, Hushai’s goal was to “nullify” (New Jewish Publication Society’s Tanakh), “thwart” (Knox), or “undo” (New American Bible) the advice given by Ahithophel. David knew that Ahithophel was a very intelligent person and that he would give advice that would be helpful to Absalom. Hushai was therefore sent to counteract that advice.
Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on the First and Second Books of Samuel, Volume 2. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here .
