The Koren Talmud Bavli, Noé Edition, Vol 6: Pesahim Part 1, Large, Color

Tractate Pesahim is classically divided into two sections. The first, tractate Pesah Rishon, discusses the laws of the festival of Matzot, including the prohibition of leaven, its elimination from one’s possession, and the mitzva to consume matza. The second, tractate Pesah Sheni, deals with the festival of Pesah and the laws of the Paschal lamb. Some suggest that it is for this reason that the tractate as a whole is entitled Pesahim, the plural of Pesah, since it includes within it these two tractates of Pesah.