The verse states that the covenant with Israel was made with those present and all their future descendants. In a similar vein, the Sages teach that all future prophecies were already transmitted at Sinai, and moreover that all the novel ideas that Torah scholars have introduced and are destined to introduce throughout the generations were given then.

Rabbi Yitzhak said: What the prophets are destined to prophesy in each and every generation was received at Mount Sinai, as Moses said to Israel: “Rather, with him who is here with us standing today…and with him who is not here with us today” (Deuteronomy 29:14).

Likewise the verse states: “The prophecy of the word of the Lord to Israel in the hand of Malachi” (Malachi 1:1). “In the days of Malachi” is not stated; rather, “in the hand of Malachi.” As, the prophecy was in Malachi’s hand from Mount Sinai, but until that time, permission was not granted him to prophesy to others. Likewise, Isaiah said: “From the time that it was set, there I was” (Isaiah 48:16). Isaiah said: From the day that the Torah was given at Sinai, I was there and I received this prophecy…until now, permission was not granted him to prophesy to others.

It was not only the prophets who received their prophecy from Sinai, but also the Sages who stand in each and every generation; each and every one of them received his interpretations from Sinai. (Shemot Rabba 28)