Red Heifer

 Kli Yakar (Bamidbar 19:21) Why the red heifer, which purifies the impure, would make the pure impure. We find that no food is susceptible to impurity until water falls upon it. How is it possible that water, whose source is purity, would cause impurity? The explanation of the matter is as follows: It is natural that everything is only affected by its opposite, not by what is of its own kind. This is similar to how the evil inclination provokes Israel more than the nations, and Torah scholars more than anyone else, because they are all opposite to it, therefore it wants to overcome them. This is the reason why darkness intensifies just before dawn, because everything is affected specifically by its opposite. Therefore, no food or seed is affected by impurity to make an impression until water, which is all purity, comes upon it. Then the impurity wants to defeat the purity, overcomes it, and makes an impression on it. Similarly, the water of sprinkling contains water which is all purity, and the ashes of the red heifer which is all impurity, and they are mixed together. Therefore, if the water of sprinkling is thrown on an impure person, the person is not affected by the ash because it is of his kind both being impure, but he is affected by the water which is opposite to him, because he is impure and the water is pure. Therefore, the water acts upon him and overcomes the impurity. But a pure person who carries the water of sprinkling is not affected by the water because it is of his kind, as both are pure, but he is affected by the ash which is opposite to him, because he is pure and the ash is impure. Therefore, the ash acts upon him and makes an impression to make him impure.