John Gill Commentary 2 Chronicles 35:14

"And afterward they prepared for themselves, and for the priests, because the priests the sons of Aaron [were busied] in offering the burnt-offerings and the fat until night: therefore the Levites prepared for themselves, and for the priests the sons of Aaron." — 2 Chronicles 35:14 (ASV)

And afterwards they made ready for themselves, and for the
priests
The passover lambs, and such parts of the peace offerings that belonged to them:

because the priests the sons of Aaron were busied in offering
burnt offerings ;
such as are before said to be removed or separated for that purpose:

and the fat ;
of the peace offerings that was to be burnt: and this employed them

until night ;
so that they could not prepare the passover for themselves:

and therefore the Levites prepared, not only for themselves, [but] and
[also] for the priests the sons of Aaron; who were otherwise engaged in the service of the day.