Albert Barnes Commentary 2 Chronicles 31:3

"[He appointed] also the king`s portion of his substance for the burnt-offerings, [to wit], for the morning and evening burnt-offerings, and the burnt-offerings for the sabbaths, and for the new moons, and for the set feasts, as it is written in the law of Jehovah." — 2 Chronicles 31:3 (ASV)

The king’s portion - Amid the widespread neglect of the observances commanded by the Law, the tithe system had naturally fallen into disuse. Hezekiah revived it, and to encourage the people to give what was due, he cheerfully set the example of paying the full proportion from his own considerable possessions (Compare to 2 Chronicles 32:28–29).

His tithe was, it seems, especially devoted to the purposes mentioned in this verse. Over the course of a year, these purposes required nearly 1,100 lambs, 113 bullocks, 37 rams, and 30 goats, in addition to vast quantities of flour, oil, and wine for the accompanying meat and drink offerings.