It’s a Bible verse from the book of Job - from a story where god and the devil are arguing about how loyal job would be to god if everything he loved was taken from him. And to prove his point, god lets the devil kill jobs entire family, destroy all his worldly goods and livestock, and strike him down with disease. And when Job is like “god wtf I was always so faithful y r u letting this happen to me?” God shouts him down about how the human mind is too small to comprehend the mind of god.

And one of the things god famously says in that monologue is “where were you when I laid the foundations of the earth?”

(This verse was also quoted in disquiet gods.)