Leviticus 14:5 - Matthew Poole's English Annotations on the Holy Bible

To wit, by some other man. The priest did not kill it himself, because it was not properly a sacrifice, as being killed without the camp, and not in that place to which all sacrifices were confined; and if it had been a sacrifice, that might be killed by another, so long as the sprinkling of the blood of it, which was the most proper and essential act in the sacrifice, was done by the priest. Over running water; it seems to be a metathesis or transplacing of words, for over running water put in an earthen vessel. Thus the blood of the bird and the water were mixed together, partly for the conveniency of sprinkling, and partly to signify Christ, who came by water and blood, 1 John 5:6. The running water, i.e. spring or river water, by its liveliness and motion did fitly. signify the restoring of liveliness to the leper, who was in a manner dead with his leprosy, as was noted before.