Albert Barnes Commentary Leviticus 17:15

"And every soul that eateth that which dieth of itself, or that which is torn of beasts, whether he be home-born or a sojourner, he shall wash his clothes, and bathe himself in water, and be unclean until the even: then shall he be clean." — Leviticus 17:15 (ASV)

This law appears to be grounded on the fact that the body of an animal killed by a wild beast, or which has died of itself, still retains a great portion of its blood. The importance ascribed to this law in later times may be seen in (1 Samuel 14:32–35); (Ezekiel 4:14); (Ezekiel 44:31), and still more in the apostolic decision regarding “things strangled,” which are pointedly connected with blood (Acts 15:20).