Deuteronomy 12:21

If the place be too far — Being obliged to carry their sacrifices to the place of worship, they might think themselves obliged to carry their other cattle thither to be killed. They are therefore released from all such obligations, and left at liberty to kill them at home, whether they lived nearer that place, or farther from it; only the latter is here mentioned, as being the matter of the scruple. As I have commanded — In such a manner as the blood may be poured forth.