John Gill Commentary 2 Chronicles 31:11

"Then Hezekiah commanded to prepare chambers in the house of Jehovah; and they prepared them." — 2 Chronicles 31:11 (ASV)

Then Hezekiah commanded to prepare chambers in the house of
the Lord
Either to build new ones, or fit up those that were built:

and they prepared [them] ;
got them ready to lay up the stores in.