The following discussion are the views of Dr Russell Harding and is not intended to be a psak on the issue.
An interesting question arose on Shabbat Re’eh concerning which Haftorah to read. On the one hand it was Rosh Chodesh Elul which occurred on Shabbat. There is a special Haftorah which is read on this occasion (it doesn’t happen often). On the other hand, we are in the seven-week period between Tisha B’Av and Rosh Hashanah. Each of these weeks has a Haftorah of consolation in which Hashem assures us that notwithstanding the bad events we remember on Tisha B’Av, He is still with us.
The question, then, is – which Haftorah should we read? Should it be Yeshayah 66:1-24 for Shabbat and Rosh Chodesh or Yeshayah 54:11–55:5 for Parashat Re’eh?
The Mishnah Berurah (Chafetz Chaim 1839–1933), the classic commentary on the Shulchan Aruch (Rav Yosef Karo, 1488–1575), addresses this question.
The Shulchan Aruch says that in this situation we should read the Haftorah for Parashat Re’eh. The Mishnah Berurah (425:5) explains that the reason for this is because we should not omit any of the seven Haftorot of consolation. The Shulchan Aruch continues, however, that there are opinions which say that the Haftorah should be the one for Shabbat and Rosh Chodesh. In the lands in which these opinions are accepted, this is the minhag.
The Mishnah Berurah explains further that the reason these opinions are accepted is that the Haftorah for Rosh Chodesh and Shabbat contains references to both Rosh Chodesh and comfort over Yerushalayim. The Mishnah Berurah continues that none of the seven Haftorot of consolation should be omitted and that therefore when we read the Haftorah for Parashat Ki Tetsei in two weeks, we append the Haftorah for Parashat Re’eh to it.
This is the Ashkenaz Minhag and is what we did on Shabbat Re’eh. Come along on Shabbat Ki Tetsei to hear the Haftorah for Parashat Re’eh.