Kommentar zu Schemot 15:18

לעלם ועד The word ועד is an expression denoting ETERNITY — The ו in it is a root-letter, and consequently it is vowelled with a Patach; but in the similar word in (Jeremiah 29:23) “I am He that knoweth and am witness (ועד)”, where the ו is a servile letter (a prefix) it is vowelled with a Kametz.

THE ETERNAL SHALL REIGN FOR EVER AND EVER. Moses is saying that just as He has now shown that He is King and Ruler by having brought deliverance to His servants and destruction upon those that rebel against Him, so may it be His will to do so in all generations forever, that He withdraw not His eyes from the righteous,²²²Job 36:7. nor hide them [His eyes] from the wicked ones who inflict evil upon others. There are many verses that are to be interpreted in this way, such as: The Eternal will reign for ever, thy G-d, O Zion, unto all generations. Hallelujah;²²³Psalms 146:10. Blessed be the Name of the Eternal from this time forth and for ever;²²⁴Ibid., 113:2. And the Eternal shall be King over all the earth.²²⁵Zechariah 14:9.
Now Onkelos was apprehensive [of translating this verse literally, which is stated in a future tense], since G-d’s sovereignty is [indeed] to all eternity [and no prayer for its continuance is possible]. Therefore he rendered it in the present tense: “The Kingdom of the Eternal endureth for ever and to all eternity,” just as is expressed in the verse, Thy Kingdom is a Kingdom for all ages.²²⁶Psalms 145:13. But I have not understood Onkelos’ opinion in this matter, for it is written: May the Glory of the Eternal endure for ever;²²⁷Ibid., 104:31. And let the whole earth be filled with His Glory;²²⁸Ibid., 72:19. “Magnified and sanctified shall be [His great Name]”;²²⁹From the beginning of the Kaddish prayer. In Ricanti’s work on the Torah in quoting this text from Ramban, he writes clearly: “and in the Kaddish [we say], ‘Magnified, etc.’” It is thus to be noted that the Kaddish-text is quoted by Ramban amidst Scriptural verses as authority for his thesis! The great sanctity of the Kaddish prayer is thus clearly indicated. Yea, let it be established, and let Thy Name be magnified for ever.²³⁰I Chronicles 17:24. It is possible that the meaning of these [future tenses] is similar to the secret of the benedictions.²³¹“Magnifying G-d’s Name brings life and blessing to the world, thus assuring that His kingdom will be acknowledged in the world in the future. And so is the purport of the benedictions we make, which begin by referring to ‘the Eternal, our G-d’ and continue to mention ‘King of the universe’” (Ma’or V’shamesh).

ה' ימלוך לעולם ועד, this too is a prayer by Moses who expresses the hope that G’d, exclusively, will reign forever, and that He will not have to share power with anyone else claiming divine authority on earth.