that it will die. What matters is slaughtering an animal while it still has life in it; it is alive even if one is certain that it will die an hour later. Thus, ʿUmar ibn al-Khattāb, may Allah be pleased with him, knew that he would die, yet he was still alive, and his will, prayers, and undertakings remained valid.
Several Companions, may Allah be pleased with them, ruled that if an animal swishes its tail, blinks its eye, or kicks its leg after slaughter, it is lawful to eat. They did not stipulate that its movements beforehand must exceed those of a slaughtered animal. The Companions said this because movement is evidence of life, but such evidence does not necessarily hold in reverse: the absence of these movements does not mean that the animal is dead. Rather, it may be alive even without displaying any such movement.
A person may be asleep and have his throat cut without struggling. Likewise, an unconscious person may have his throat cut without struggling. An animal, too, may be alive when slaughtered yet not struggle because it is too weak to move, despite being alive. However, the flow of blood of the kind that comes only from an animal slaughtered alive—not the blood of a dead animal—is evidence of life. And Allah knows best.