Rashi on Deuteronomy 5:19/רש"י על דברים ה׳:י״ט

1ולא יסף — We render this in the Targum by ולא פסק “and He did not cease”, — [Because it is characteristic of human beings that they are unable to utter all their words in one breath (but must make pauses) and it is characteristic of the Holy One, blessed be He, that this is not so, therefore He did not pause, and since He did not pause, He did not have to resume], — for His voice is strong and goes on continuously (Sanhedrin 17a). Another explanation of ולא יסף: He did not again ever reveal himself with such publicity.