Yerushalmi Megillah 4:2 ירושלמי מגילה ד׳:ב׳

MISHNAH: On New Moon’s Days and on the intermediate days of holidays four are reading, no less and no more, and one does not close with a reading from Prophets. The ones who start and finish the Torah reading recite the benediction before and after the reading⁷¹The one who starts recites the benediction before and the one who ends recites the benediction after, according to the old standard abolished in Amoraic times.. This is the principle: four are reading on any {day} when there is musaf⁷²Either referring to Temple times, a musaf sacrifice as prescribed in Num. 28–29, or in Mishnaic times a musaf prayer after the reading from the Torah. and it is not a holiday.

HALAKHAH: ⁷³This is repeated (mostly by the corrector) from Ta`aniot 4:3, Notes 141–148. Rav Ḥuna said, three people reading in the Torah shall not do less than ten verses. Ḥizqiah said, corresponding to the Ten Commandments [But did we not state, “on Sunday, In the Beginning and there shall be a spread”? And these are only eight! Rebbi Idi said, Cahana and Assi disagreed. One said, he repeats. But the other said, he splits. He who says that he repeats, he repeats two verses. He who says he splits, he splits it was evening, it was morning, as a separate verse. But did we not state, “on Monday, there shall be a spread and the waters shall come together”? He who says that he repeats, he repeats two verses. He who says he splits, he could not split. Rebbi Philippos ben Protos objected before Rebbi Jonah, is there not the paragraph about Amalek? He said to him, there is a difference since this is the topic of the day.] Rebbi Eleazar from Merom asked, was it not stated, the one who reads the conclusion from Prophets should not do less than 21 verses. Should there not be 23? Three for ten, three for ten, and one three⁷⁴He reads the statement of Rav Huna to mean that any time three people read in the Torah they together must read 10 verses. Then on a Sabbath, when 3+3+1 readers are called, they must read a minimum of 23 verses. Corresponding to this the reader from Prophets should have to read 23 verses. The fact that he has to read only 21 shows that we have to read Rav Huna’s remark as referring only to the weekday and Sabbath afternoon readings..