Midrash su Levitico 23:37

7) R. Akiva says: What is the intent of (Vayikra 23:37) "These are the festivals of the L–rd which you shall call them holy callings"? If to the days of the festival (proper), these are already mentioned, viz. (Vayikra 23:39) "on the first day, a resting, and on the eight day, a resting. If so, what is the intent of "which you shall call them holy callings"? These are the intermediate days of the festival, on which (non crucial) labor is forbidden.

26 (Numb. 29:35) “On the eighth day”: What was the reason for [the number of sacrificial animals] being reduced on each day? The Torah is simply teaching you etiquette from the sacrifices. Thus if someone goes for lodging,²²Gk.: Xenia. and his host receives him; on the first day he receives him properly and feeds him fowl. Then on the second he feeds him meat; on the third he feeds him fish; on the fourth he feeds him greens. So does he continue to reduce, until he is feeding him pulse. (Numb. 29:35) “You shall have (literally, there shall be for you)”: What is the meaning of “for you?” [The Holy One, blessed be He,] said to them, “Festival times are fitting for you.” A certain gentile questioned R. Aqiva. He said to him, “Why do you keep festival times? Did not the Holy One, blessed be He, say the following to you (in Is. 1:14), ‘Your new moons and your festival times My soul hates?’” R. Aqiva said to him, “If He had said, ‘My new moons and My festival times My soul hates,’ I should have said [so. But] He said, ‘Your new moons and your festival times’; because of those festival times which Jeroboam instituted, as stated (in I Kings 12:32-33), ‘Jeroboam also instituted a festival on the fifteenth day of the eighth month, like the festival in Judah, at Bethel to sacrifice to the calves. And he ascended the altar […] and he made a festival for the Children of Israel […].’ These festival times, however, (the ones ordained by the Holy One, blessed be He,) shall never be abolished. Neither shall the new moons. Why? Because they belong to the Holy One, blessed be He, as stated (in Lev. 23:37), ‘These are the festival times of the Lord.’ And similarly (in Lev. 23:4), ‘These are My festivals times.’” And it is also written (ibid. verse 44), “And Moses told the festival times of the Lord.” They shall, therefore, never be abolished; for it is concerning them that it is stated (in Ps. 111:8), “They are established forever to be performed with faithfulness and uprightness.”

(Devarim 12:5) "and you shall come there … (6) and you shall bring there": Why is this stated (i.e., it is essentially stated elsewhere). Because it is written (Vayikra 23:37) "These are the festivals of the L-rd, which you shall call holy callings to present a fire-offering to the L-rd, a burnt-offering and a meal-offering, sacrifice and drink-offerings, the thing of the day in its day."