«يَا حَارِثُ، أَمَعَنَا ثَالِثٌ؟»
Al-Ḥārith, is there a third person with us?
Before continuing, Abū Zayd asks who else is present. The initial a- forms a question and maʿanā means “with us.” The question matters because he is about to disclose something that he prefers not to reveal before a stranger.