From the rulings of Ahl adh-Dhimmah
“…1 – Honoring the Muslims in their gatherings, and to not plot against them, and to not enter upon them without their permission, and to not act impolitely or disrespectfully in their presence, and to greet them with the best of greetings, and to not extend their feet or raise their voices in their presence.
2 – To rise for the Muslims in their own gatherings; meaning: if they enter upon us (the people of dhimmah) while we are in a gathering, then we get up from our places and offer them to the Muslims instead, so that they would have the best spots and we would have the farthest.
And this includes gatherings that are both mixed (containing Muslims and non-Muslims) as well as exclusive (only non-Muslims). So, if they enter upon them in their churches, for example, then they are to get up from their places and sit them (the Muslims) down in their place.
[‘Ahkam Ahl adh-Dhimmah’; p. 527]