The very last Mishna in the massekhet deals with the various blessings made when eating the sacrifices at the seder during the Temple period. Can the general berakha on the korban hagiga brought for the holiday cover the korban Pesah, as well, or does each need its own berakha? According to the Mishna, this question is debated by Rabbi Yishmael, who believes that one may cover the other, and Rabbi Akiva, who believes that, under all circumstances, each will need its own berakha.
From this discussion the Gemara segues to a question about pidyon ha-ben – redeeming the first-born.
Rabbi Simlai attended a redemption of the firstborn son. The celebrants raised a dilemma before him with regard to the blessings. First they noted that it is obvious that the blessing over the redemption of a first born son, which is: Who sanctified us with His mitzvot and commanded us over the redemption of the firstborn son, is certainly recited by the father of the son, as he is the one obligated to redeem his son. However with regard to the second blessing: Blessed are You, Lord our God, King of the universe, Who has given us life [sheheheyanu], sustained us, and brought us to this time, does the priest recite this blessing, or does the father of the son recite it?
The Gemara concludes that the question was presented to the scholars in the Bet Midrash and they ruled that the father makes both berakhot.
The Nemukei Yosef explains the question as follows: On the one hand, the father who is performing the mitzva is doing it with some financial outlay, so perhaps the kohen should say it, since his participation involves only benefit to himself. On the other hand, in this case the father is enjoying something that goes well beyond the performance of a mitzva. Since the pidyon ha-ben takes place only after 30 days, when we are certain that the baby has reached a level that he will not be considered a nefel (stillborn), there is certainly an additional element of joy for the father.
The Rashash comments on this Gemara that really both parties should be saying she-heheyanu, each for their own reason. The Gemara’s question is which of them has a greater level of obligation, so that he should say it on behalf of both participants.