Charles Ellicott Commentary 2 Chronicles 35:8

"And his princes gave for a freewill-offering unto the people, to the priests, and to the Levites. Hilkiah and Zechariah and Jehiel, the rulers of the house of God, gave unto the priests for the passover-offerings two thousand and six hundred [small cattle], and three hundred oxen." — 2 Chronicles 35:8 (ASV)

And his princes ... Levites. — And his princes for a free-will offering (Leviticus 7:16) to the people, to the priests, and to the Levites had presented heave-offerings. How many victims they gave is not specified. Some words may have fallen out of the text. (Compare to 2 Chronicles 30:24.) Hilkiah is introduced quite abruptly in the text as it stands.

Rulers of the house of God. — 2 Chronicles 31:13; 1 Chronicles 9:11. Hilkiah was high priest (2 Chronicles 34:9); Zechariah perhaps his deputy, the second priest (2 Kings 25:18); Jehiel may have been the head of the line of Ithamar, which still existed even after the return (Ezra 8:2).

Oxen, i.e., bullocks (2 Chronicles 35:7).