“Ḥattā idhā kuntum fī al-fulki wa-jarayna bihim bi-rīḥin ṭayyibah”
“When you are in the ships and they sail with them by a favorable wind.” (Yūnus 10:22, excerpt)
“Kuntum” addresses the hearers directly as “you”; “bihim” shifts to “them.” The audience first enters the scene and then sees the travelers as people being described. The referent remains connected even though the grammatical viewpoint changes.
This shift is called iltifāt. It refreshes the discourse and makes the picture vivid. It should not be misconstrued as proof that an entirely unrelated group has suddenly appeared.