And the LORD shall be king over all the earth: in that day shall there be one LORD, and his name one.
And the Lord shall be King over all the earth. Isaiah 54:5 implies that this is to be the consequence of Israel being again recognized by God as His own people. For after saying "Thy Maker is thine husband ... and thy Redeemer the Holy One of Israel" the prophet states, as the consequence, "The God of the whole earth shall He be called" (Daniel 2:44; Revelation 11:15).
In that day shall there be one Lord, and his name one - not that He is not so already, but He shall then be recognized by all unanimously as "One." Now there are "gods many and lords many." Then Yahweh alone shall be worshipped. The manifestation of the unity of the Godhead shall be simultaneous with that of the unity of the Church. Believers are one in spirit already, even as God is one (Ephesians 4:3-6). But externally there are sad divisions. Not until these disappear shall God reveal fully His unity to the world (John 17:21; John 17:23). Then shall there be "a pure language, that all may call upon the name of the Lord with one consent" (Zephaniah 3:9). The Son too shall at last give up His mediatorial kingdom to the Father, when the purposes for which it was established shall have been accomplished, "that God may be all in all" (1 Corinthians 15:24).