Halakhah sur Jérémie 2:4

On the three Shabbosos between the seventeenth of Tammuz and Tishah beAv, we read the "Three haftaros of retribution," which are: Divrei Yirmiyahu (The words of Jeremiah) (Jeremiah 1:1), Shim'u devar Hashem, (Hear the word of Hashem) (Jeremiah 2:4), Chazon Yeshayahu, (The vision of Isaiah) (Isaiah 1:1). Their initials form the acronym DeShaCh. If, by mistake, the reader recited on the first Shabbos the haftarah of the weekly portion, on the second Shabbos, he should read the haftarah of both Divrei Yirmiyahu and Shim'u, because they are close to each other. If Rosh Chodesh Av occurs on Shabbos, he reads the haftarah Hashamayim Kis'i (The heaven is My throne) (Isaiah 66), but in some communities, the haftarah Shim'u is read.

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.)