The 2002 LDS booklet titled Preparing to Enter the Holy Temple states:
If we would understand both the history and the doctrine of temple work we must understand what the sealing power is. We must envision, at least to a degree, why the keys of authority to employ the sealing power are crucial.
Nearly nine hundred years before Christ, the prophet Elijah appeared in the court of the king of Israel. He carried with him a sacred authority: the power to seal.