Halakhah sa Isaias 1:14: Mishneh Torah, Prayer and the Priestly Blessing & Shev Shmateta

On the first day of each month, the person first called to the reading of the Law reads three verses from the section beginning Tzav (Numbers 28:1-8). The second person called to the Law repeats the third verse already read by the person called before him and adds the two following verses, so as to leave three verses to the end of the section. The third person called to the Law reads these three verses and also the next section beginning Uveyom Hashabbath (ibid. 28:9-10). The fourth person called to the Law reads the section beginning Uvrashé Chodshechem (ibid. 28:11-15). When the first of the month falls on a Sabbath, two scrolls of the Law are taken out during the morning service. In the first, the portion for the week is read; and in the second, the one who completes the reading reads Uverashé Chodshechem (Numbers 28:11-15). The person who reads the lesson from the Prophets is the one who reads the section concerning the New Moon. The lesson from the Prophets is that section which concludes, "And it shall come to pass that month by month etc." (Isaiah 66:23). When the first of Ab falls on a Sabbath, the lesson from the prophets is the section containing the verses, "Your new moons and your festivals my soul hateth" (ibid. 1:14). When the first day of the month falls on the first day of the week the lesson from the prophets on the preceding Sabbath day is the section beginning, "And Jonathan said unto him; tomorrow is New Moon" (I Samuel 20:18-42).

(Samekh) ‘Paved is the path of the straight’ that walk ‘in the way of charity,’ which is [what provides for] the maintenance of the world. ‘Happy is the one who reflects upon the destitute,’ and especially on the day of a joyful party and a holiday, as it is elucidated in the Zohar 2: 88b. And these are its words:
Come see that on all the other times and festivals, a man must rejoice and make the poor rejoice. And if he rejoices alone and does not give to the poor, his punishment is great, etc. About him it is written (Mal. 2:3), “And I will strew dung upon your faces, the dung of your festivals.” But if he rejoices on Shabbat – even though he does not give to the other – He does not give him a punishment like the other times and festivals, as it is written, “the dung of your festivals,” and not “the dung of your Shabbats.” And it is [also] written (Isaiah 1:14), “Your new moons and your holidays My soul does hate,” but Shabbat is not mentioned. And for this reason, it is written (Exod. 31:17), “Between Me and between the Children of Israel.” To here [are its words].
[However we need to understand] the reason that on festivals one needs to make the poor rejoice more then on Shabbat; and also what is the relevance of new moons here, such that it is written, “Your new moons and holidays My soul does hate,” whereas in the Zohar it is not mentioned that one needs to rejoice on new moons; and also that which it says, “And that is what is written, ‘Between Me and between the Children of Israel.’” It appears to me that the holy days are supernal guests, and one needs to make the guests rejoice. And this is their joy – to have the miserable poor rejoice. From this they take their portion. In order to grasp the point of the matter, I will tell you a parable about a king who visited a villager under his rulership. And [the villager] recognized him, but did not put his attention to honoring him properly. And [so] the king got angry with him. But when [the king] raised his eyes, a messenger came to him sent by another villager. [The message was], “If it would be good for the king, let him come to a party that I will make for him.” And [so] he came to the house of that man. But behold that man also did not pay attention to the king, and he also did not honor him. Then ‘the king broke out into a great anger.’ He said ‘with rage and fury,’ “[He] ‘shall be [torn by his] limbs and his home shall be a dunghill,’” as the act of this one was worse than the first man. [That is] because the king came to the first on his own, whereas this one sent for him. And the king also got angry at the messenger, as he was the [immediate] cause of his embarrassment. And behold, on Shabbat which is ‘fixed and standing’ and the [supernal] guests come on their own, He does not punish [those that do not share with the poor] much. But [this is not the case] on festivals and holidays which are [set] by Israel, like the statement of [the Sages], may their memory be blessed, “‘Which you shall proclaim them (otam)’ (Lev. 23:2) – [do not] read [‘them,’ but rather], ‘you (atem)’” (Rosh Hashanah 24a). And if one does not honor the guests then, his punishment is great. For this reason, it stated, “Your new moons and holidays My soul does hate” – since the [holidays] are [established by way] of the new moons, and He gets angry with the messenger as well. And for this reason, it said, “And that is what is written, ‘Between me and between the Children of Israel.’” [This is] since Shabbat is ‘fixed and standing,’ and we accordingly say (in the holiday prayers), “Who sanctifies the Shabbat, Israel and the [holidays]” – as Shabbat is a sign between Him and the Children of Israel, whereas the festivals are a sign between the Children of Israel and Him. And [it is also] because the Shabbat is ‘fixed and standing,’ whereas holidays are [established] by Israel. And understand [this]. And [it is] also because one needs to appear before the Lord on festivals and [holidays] – as it is stated (Deut. 16:16), “all your males shall appear” – [hence] at least at these times, he should be in the image and the likeness, the rich and the poor, together. And [he should then] not, God forbid, be like a beast.