A passage from the Prophets recited after Torah reading.
Traditionally, on Shabbat and holiday mornings, a selection from one of the biblical books of the Prophets is read after the Torah reading. The portion is known as the haftarah (hahf-tah-RAH, or in Ashkenazic Hebrew: hahf-TOH-rah). On two fast days, Yom Kippur and Tisha B'av, a haftarah is recited at both morning and afternoon services.
While the Torah reading cycle proceeds from Genesis through Deuteronomy, covering the entire Five Books of Moses, only selected passages from the Prophets make it into the haftarah cycle. A cluster or three or four berakhot (blessings), depending on the occasion, follows the haftarah. Their call for prophecy to be fulfilled and for God to restore the Jewish people to Zion serve as a finale to the full set of the day's scriptural readings, Torah and Haftarah together.
Prophets of Truth and Justice
Rabbinic literature does not discuss the origin of the practice of reading publicly from the Prophets in a formal cycle. We might look to the liturgical setting of the haftarah, then, for some clue about its intended function. In addition to berakhot recited after the portion, every haftarah is introduced with a berakhah praising God for having "chosen good prophets and accepted their words, spoken in truth."
The formula goes on to note that God shows favor to "the Torah, Moses His servant, Israel His people, and the prophets of truth and justice." This focus on the reliability of the Israelite prophets has led some scholars in the late 19th and early 20th centuries, including Adolf Büchler and Abraham Zevi Idelsohn, to speculate that the institution of the haftarah originated in bitter polemics among competing religious groups in Ancient Israel--the Jews and the Samaritans.
The Samaritans were then an ethnic group rivaling the Jews in numbers, power, and influence. The Samaritans insisted on the exclusive truth of the Torah (their version differs somewhat from the Jewish Torah) and rejected all prophets after Moses. That rejection could well have formed the background for the practice of reading from the Prophets in synagogues. By declaring the prophetic books authoritative and their origin divinely inspired, the Jews may have sought to exclude Samaritans from local communities and offer a statement of opposition to a major tenet of Samaritan theology. This view is now accepted widely, but not universally, among scholars of Jewish liturgy.