I can’t remember exactly the name, but I heard of a language used by gods, wich is understandable by every sentient being. It directly form the concept in the auditor’s mind (thus, you can adress everybody at the same time, even if they’re from different origins/species/etc).
It can not be learned and is reserved to superior entity to communicate with mortals (so it’s probably not the Celestial)
Now, let’s say for story’s sake, that a mortal does know it (for GM-ing reasons). Does the ability to speak God’s language grant him the ability to understand other sentients beings, speaking differents language?
First, I would say no, as the mortal doesn’t know other languages. But how do gods understand their followers in that case? Heavy use of “Comprehend Languages” spell?