Halakhah for Isaiah 61:10

The custom on a Shabbos where a groom is present is to recite after the Haftarah [The word "Haftarah": some say it is [related to] the phrase "Ain maftirin achar hapesach" ("We do not eat anything after the [korban] pesach"), which means to remove (ie. which signals the end); meaning, it is the removal/ending of the morning prayers] of that week, two or three verses from the Haftarah "Sos Asis" ("I greatly rejoice" - Isaiah 61:10). And when Rosh Chodesh falls out on Shabbos and Sunday, after we recite the Haftarah for that Shabbos, we recite the first and last verse of the Haftarah "Va'yomer Lo Yehonatan, machar chodesh" ("And Yehonatan said to him 'tomorrow will be the new moon'" - Samuel 20:18). And one should not protest [this custom]. (And see below in siman 425 se'if 3, and the end of siman 428 for what our custom is.)