122:6 On the three Shabboses between the 17 Tamuz and Tisha b’Av, we read the three haftaros of retribution: “The words of Jeremiah…” (Jeremiah 1:1), “Hear the word of Hashem…” (Jeremiah 2:4) and “The vision of Isaiah…” (Isaiah 1:1). The mnemonic acronym for these haftaros is daled-shin-ches. If one made a mistake and read the normal weekly haftarah on that first Shabbos, then both “The words of Jeremiah…” and “Hear the word of Hashem…” are read on the following Shabbos, since they are close together in Tanach. If Rosh Chodesh Av falls on Shabbos, we read “The heaven is My throne…” (Isaiah 66), though some communities read “Hear the word of the Lord….” (The Rema – OC 425:1 – says that if a community does not have a custom, they should follow the prevalent practice and read “The heaven is My throne…” The Gra disagrees and says to recite “Hear the word of the Lord….” – Mishnah Brurah 425:8.)
122:7 When the month of Av arrives, we reduce our joy. We do not build a house for joyful reasons or a building only for benefit. (A shul may be built because it is a mitzvah for the masses – Mishnah Brurah 551:12.) If one hired a non-Jew to plaster his house, if one can pay him a small fee to delay the work until after Tisha b’Av, he should do so. If this is not possible, then the work is permitted. A Jew who has a legal matter against a non-Jew should try to postpone it because this is considered an inauspicious time. If possible he should postpone it until the month of Av is over, or at least until after Tisha b’Av. We do not recite the blessing on the moon until after Tisha b’Av.