Initially, the Torah was read on the Sabbath or special occasions by the king, a prophet, or a kohen. In time, distinguished people were called to read portions of the Torah. The Torah was on a platform to which the reader ascended, hence the Hebrew term aliyah ("going up"). Eventually, the rabbis ordained that a professional reader do the reading to avoid embarrassing those who were unable to read the Torah script (Shabbat 11a). There are seven aliyot on a Sabbath (Megillah 21a). Bet Yoseph quotes a geonic source in explanation of this number (Ein Pochasim, Tur, Hilchot Shabbat 282). In the event that someone missed an entire week's services and as a result had not responded to the reader's daily invocation of Barechu, he may make up for it by responding to the Barechu of the seven blessings of the aliyot. A more acceptable reason is the midrashic explanation for the seven benedictions on the Sabbath (in place of the eighteen). The seven benedictions correspond to the seven voices of God (kol) mentioned in the Twenty-ninth Psalm and again in connection with the giving of the Torah (beginning with Exodus 19:16, Midrash Yelamdenu). This explanation is equally applicable to the seven aliyot. The first aliyah is assigned to a kohen and the second to a levi. This order was ordained to avoid public competition for the honor of being first (Gittin 59b). Babylonian Jewry completed the reading of the Torah within one
year. Palestinian Jewry adopted a triennial cycle (Megillah 29b). The reading of a selection from the Prophets originated in the time of the Mishnah (Megillah 24a). This practice probably began after the canonization of the Bible and the ensuing effort to highlight the Prophets.〔Bloch, Abraham P., The Biblical and Historical Background of Jewish Customs and Ceremonies, KTAV Publishing House, Inc., 1980, p.134〕