Rabbi Eliezer says that the eglah (beheaded when a body is found between cities) is one year old and the parah (red heifer) is two years old. The Sages say that the eglah is two years old and the parah is three or four years old. Rabbi Meir says that the parah may even be five years old, though they wouldn’t wait that long since it might develop black hairs and become unfit. Rabbi Yehoshua said that he only heard of a “shlashis” (i.e., a cow three years old) being used. The Sages asked Rabbi Yehoshua why he used the term “shlashis” (rather than “shlishis”). “I don’t know,” he replied. “I was taught it that way without any explanation.” Ben Azzai explained that “shlishis” means “the third” when counting, while “shlashis” means three years old. Similarly, they referred to a vineyard as “revai.” The Sages asked Rabbi Yehoshua about “revai” and he replied, “I was taught it that way without any explanation.” Ben Azzai explained that “revii” means fourth when counting, while “revai” means four years old. Similarly, they discussed one who ate half a loaf, three of which can be made from a kav, in a nega-infected house. The Sages asked Rabbi Yehoshua why he didn’t just say “eighteen of which can be made from a seah.” He replied, “I was taught it that way without any explanation.” Ben Azzai explained that when you say “three of which can be made from a kav,” it would not include challah (which is not taken from so small a volume of dough); when you say, “eighteen of which can be made from a seah,” the volume of the dough is reduced by the challah that is taken.
Rabbi Yosi HaGlili said that bulls (for offerings) are two years old as per Numbers 8:8, “You shall take a second young bull for a sin-offering.” (“Second” is taken to mean two years old.) The Sages say the bulls may be even three years old. Rabbi Meir says they may even be four or five years old but animals that old are not brought as sacrifices out of respect.