Halakhah su Numeri 28:9

In the morning we arise early to the Synagogue and we arrange the blessings, the biblical paragraphs of the sacrifices, and the Mishanayos of (the Chapter) אֵיזֶהוּ מְקומָן (What is the Location, Zevachim Perek 5) like the order of the other days only we add וּבְיום הַשַּׁבָּת (And on the Sabbath Day, Bamidbar 28:9-10). And we say בָּרוּךְ שֶׁאָמַר (Blessed is the one that said) and 'Pesukei Dezimra' (Verses of Song), and we are accustomed to add Psalms because there is no work for the Nation.

The commandment of the additional sacrifice of Shabbat: That Israel was commanded to sacrifice two lambs [as a] sacrifice on every Shabbat day, in addition to the regular sacrifice of every day. And it is called the addition of Shabbat, as it is stated (Numbers 28:9), "And on the Shabbat day, two lambs, etc."

Laws of Rosh Ḥodesh that happens to fall on Shabbat, which has three clauses: On Rosh Ḥodesh that happens to fall on Shabbat, for the 'aravit, shaḥarit, and minḥah services pray the regular seven blessings, but say Ya'aleh v-Yavo in the 'avodah prayer, and it is not necessary to menton Shabbat in the Ya'aleh v-Yavo. And take out two Torah scrolls, and read from the first the seven regular readings for the day, and from the second read the mafṭir — "and on the Sabbath day" and "and on your new moons" until the end of the portion, Numbers 28:9-15. And as a prophetic conclusion read Isaiah 66, "The heavens are My throne" except for Rosh Ḥodesh Elul that falls on Shabbat, on which we read Isaiah 54:11–55:5, "Unhappy, storm-tossed..." (Rema: And some do say Isaiah 66, and thus is the custom in our lands, but on Rosh Ḥodesh Av that falls on Shabbat we as a prophetic conclusion read the portion starting with Jeremiah 2:4, "Hear ye," and this is the general practice where there is no custom. And if Rosh Ḥodesh happens upon one of the four special Shabbatot, we read the final prophetic reading for that reading, and see below, siman 785.)