What are the differences between the pesach offered in Egypt and the pesach-offering of [succeeding] generations? —- The purchase of the Egyptian pesach was on the tenth [of Nissan], it required sprinkling [of its blood] with a bundle of hyssop upon the lintel and upon the two doorposts, and was eaten in haste, during one night; but the Pesach of [succeeding] generations is observed all seven days.

Said R' Yehoshua, “I have heard that the substitute of a pesach is offered, and that the substitute of a pesach is not offered, but I cannot explain [it].”  Said R' Akiva, “I will explain”: [If] the [original] pesach-offering was found before the slaughtering of the [substitute] pesach, it must be left to pasture until it develops a blemish, is [then] sold, and a peace-offering is bought with its proceeds, and so is [the rule regarding] its substitute. [But if it was found] after the slaughtering of the [substitute] pesach, it is offered as a peace-offering, and so is [the rule regarding] its substitute.

[If] someone designates a female [animal] for his pesach offering, or a male in its second year, it must be left to pasture until it develops a blemish, and is sold, and its money is [placed in] a donative offering [chest].  [If] one had designated his pesach-offering and [then] died, his son who inherits it may not bring it as a pesach-offering, but rather as a peace-offering.

[If] the pesach-offering was confused with [other] offerings, they must all be left to pasture until they develop blemishes, and are sold. Then he should bring this type of offering equivalent in value to the best of them, and he should bring the other type of offering equivalent in value to the best of them, and he must cover the added cost from his own purse.  [If] it was confused with firstborn-offerings —- R' Shimon says: If the group is composed of Kohanim, they may eat (the offerings).