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/translate/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/translate/figs-simile]] and [[rc://en/ta/man/translate/figs-parallelism]])
The wicked consider darkness to be their light, because they do their evil deeds in the darkness and they are familiar with the darkness. (See: [[rc://en/ta/man/translate/figs-irony]])
The raised arm of the wicked represents their power and intention to do evil things, but the wicked stop doing those evil things when the morning light comes. (See: [[rc://en/ta/man/translate/figs-metaphor]])