Simple RAW for 5e V: The Disadvantage Strikes Back

[AHF]

A58

The moment the Priest deals damage with Spirit Guardians. That's one of the conditions that make Sanctuary end and the first one to happen in the order provided.

I may be missing something but I don’t see doing damage as a condition that makes Sanctuary end:

“If the warded creature makes an Attack or casts a spell that affects an enemy creature, this spell ends.”