What is the interpretation of each of "a clear verse or an established Sunnah or a just obligation," which was said to be the best of knowledge?

This Hadith is weak: "Knowledge is three, and all else is a surplus: a definitive verse, an established Sunnah, or a just ordinance." The definitive verse is that which is not abrogated. The established Sunnah is that which is authentically proven from the Messenger, peace and blessings be upon him. The just ordinance is every ruling that achieves justice. And it was said: everything that must be acted upon, and it is a reference to scholarly consensus (Ijma') and analogical reasoning (Qiyas).