Charles Ellicott Commentary Leviticus 14:5

"And the priest shall command to kill one of the birds in an earthen vessel over running water." — Leviticus 14:5 (ASV)

And the priest shall command that one of the birds be killed. —Rather, And the priest shall command, and he shall kill the one bird. This means that, upon the priest ordering it, the cured leper is to kill the one bird that is the fairer and better of the two, as was the rule during the Second Temple. Not being a sacrifice, the victim was killed outside the camp.

In an earthen vessel over running water. —Better, over an earthen vessel upon (or into) living water, meaning the bird was killed over the dish, so as to let the blood flow into the water.

The vessel had to be a new one; into it was poured a fourth part of a log, or as much as an egg and a-half, of “living water.” The term “living water” signifies water taken from a running stream or a perennial spring, where its continual motion resembles life, in contradistinction to stale or stagnant water.

Water that had already been used for other purposes, salt water, rainwater, or water that had been melted or warmed, was illegal. When the blood had thus been wrung into it, a hole was dug, and the bird was buried in the presence of the priest and the patient.