It is easy to say, "Give, give" and then see how people respond before you actually give. But Hezekiah gave out of his own possessions (2 Chrn 31:3-5) before he issued the command for other people. As one who admonishes people weekly, it is important that I be doing the very things I am asking other people to do. It only makes sense. While yes, the people should have been giving to the Temple, and yes, they should have been offering sacrifices regardless of what the king is doing, but the king should have been doing this as well. Hezekiah is not playing the "I'll do it if you go first" game; he is working through his own heart first and then 'inviting' (read: ordering, he is the king after all) others to join him.