2 Chronicles 30:16

After their manner - According to the Mishna, the custom was for the priests to stand in two rows extending from the altar to the outer court, where the people were assembled. As each offerer killed his lamb the blood was caught in a basin, which was handed to the nearest priest, who passed it on to his neighbor, and he to the next; the blood was thus conveyed to the altar, at the base of which it was thrown by the last priest in the row. While basins full of blood were thus passed up, empty basins were passed down in a constant succession, so that there was no pause or delay.

Which they received of the hand of the Levites - Ordinarily, the blood was received at the hand of the offerer. But the greater number of the Israelites 2 Chronicles 30:17 who had come to keep the feast were involved in some ceremonial or moral defilement, from which there had not been time for them to purify themselves. On account of this uncleanness, they did not slay their own lambs, but delegated the office to the Levites.