Midrash sa Levitico 23:2: Mekhilta DeRabbi Yishmael, Sifra, Devarim Rabbah & Midrash Tehillim

What is the intent of (Exodus, Ibid. 150 "And the seventh day, a Sabbath of resting, holy to the L–rd"? From (Leviticus 23:4) "These are the festivals of the L–rd, callings of holiness," I might think that just as the holiness of the festivals (i.e., the determination of their times by intercalation and the like) is relegated to beth-din, so, the holiness of Sabbath. It is, therefore written "and the seventh day, a Sabbath of resting, holy to the L–rd" — Sabbath is relegated to the L–rd, and not to beth-din. And thus is it written (Ibid. 14) "And you shall keep the Sabbath."

1) (Vayikra 23:2) ("Speak to the children of Israel and say to them: The festivals of the L–rd, which you shall call (them) callings of holiness — these are My festivals.") And whence is it derived that the year is intercalated for the sake of those living in exile, (who left their places) and have not yet reached (Jerusalem for the festival)? From "the children of Israel … The festivals of the L–rd" — Arrange the festivals so that they can be observed by all of Israel.

Another matter: “That has God near it” – Rabbi Yoḥanan said: When the ministering angels gather before the Holy One blessed be He, saying: ‘When is Rosh HaShana and when is Yom Kippur,’ the Holy One blessed be He says to them: ‘Why are you asking Me? Let us, I and you, go to the earthly court.’ From where is this derived? As it is written: “That has God near [kerovim]²⁷Plural it” – it is not written here [of God]: “Who has a nation near [Him]” but rather [it is written of Israel]: “That has God near it” – He and His entire entourage.²⁸The fact that God is described as close to Israel rather than the other way around indicates that, to a certain extent, Israel is primary. The midrash interprets this to refer to the fact that it is Israel who determines when the new month occurs, and, consequently, when the holidays occur (but see Maharzu, who suggests a textual emendation to this passage). Rabbi Yoḥanan said: The Holy One blessed be He said: ‘Until you became My nation – “the appointed times of the Lord” (Leviticus 23:2).²⁹It was God who determined the calendar. From then on – “that you shall proclaim them”’ (Leviticus 23:2).