At nighttime, people cannot see clearly, but in the morning the light reveals the distinct shape of everything, just like a seal creates distinct images in clay. (See: [[rc://en/ta/man/jit/figs-simile]])
Here "it" refers to the earth. This phrase has a similar meaning to the first phrase in this verse. (See: [[rc://en/ta/man/jit/figs-simile]] and [[rc://en/ta/man/jit/figs-parallelism]])