Halakhah do Izajasza 1:1

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.