O you who have believed, do not enter the houses of the Prophet except when you are permitted for a meal, without awaiting its readiness. But when you are invited, then enter; and when you have eaten, disperse without seeking to remain for conversation. Indeed, that [behavior] was troubling the Prophet, and he is shy of [dismissing] you. But Allāh is not shy of the truth. And when you ask [his wives] for something, ask them from behind a partition. That is purer for your hearts and their hearts. And it is not [conceivable or lawful] for you to harm the Messenger of Allāh or to marry his wives after him, ever. Indeed, that would be in the sight of Allāh an enormity.
Sahih International
يَـٰٓأَيُّهَا
yāayyuhā
O you who believe!
Word breakdown
ي
Harf · Vocative particleO!
أيُها
Ism · NounO you who believe!
Grammar rules
يَـٰٓأَيُّهَا (O you who believe!) uses the vocative — it's calling out to someone or addressing them directly.
We add "O" before the name — "O O you who believe!!"
Lesson 21 · Advanced Nasb Cases