The creator will speak to you in your voice
G-d is the totality of the Cosmos itself. It is not Human and does not "speak" from a tongue and lips nor does G-d even "think" like we do. We have a finite method of processing information. G-d's point of view would be functionally unlimited with no doubt, fear, disappointment or any other manifestation of not knowing the outcome and being surprised.
When G-d literally "speaks" it's a Human speaking directly to you.
But. Let's say G-d did somehow speak directly to someone from out of thin air. It would be in the exact vocabulary and syntax that the person could understand the best.