RobH_en_tn/num/35/33.md

Do not pollute in this way the land where you live, because blood from murder pollutes the land

Making the land unacceptable to Yahweh is spoken of as if it were physically polluting the land. Alternate translation: "Do not make the land where you live unacceptable to me in this way, because blood from murder makes the land unacceptable to me" (See: rc://en/ta/man/translate/figs-metaphor)

in this way

This means by disobeying the laws concerning a person who kills someone.

No atonement can be made for the land when blood has been shed on it, except by the blood of the one who shed it

This refers to when a person intentionally kills another person. This can be stated in active form. Alternate translation: "When someone has shed blood in the land, only the execution of the murderer can make atonement for the land" (See: rc://en/ta/man/translate/figs-activepassive)