In Berachot, 45a, at the beginning of the second chapter, the Mishnah states: “Rabbi Tarfon says that the blessing over water is Borei Nefashot Rabot.” It is not Shehakol Nihyeh Bidvaro.
Tosafot explains that Rabbi Tarfon held that the first blessing over water is Borei Nefashot, whereas the Sages held that the first blessing is Shehakol Nihyeh Bidvaro. The Gemara then says, “Go and see what the people do.” The custom is to make Shehakol as the first blessing and Borei Nefashot as the after-blessing, not in accordance with Rabbi Tarfon.
However, it is difficult to say that the dispute between Rabbi Tarfon and the Sages concerns the after-blessing. Everyone agrees that one recites Shehakol as the first blessing and Borei Nefashot as the after-blessing, and not as Rabbi Tarfon understood it. Rabbi Tarfon’s position is that Borei Nefashot is recited as both the first and the after-blessing. If so, Rav Pappa said that one recites a blessing both before and after drinking water. The Gemara challenged this from the Mishnah, which states that there are certain items over which one recites a first blessing but not an after-blessing. What is the case? Instead of challenging Rav Pappa, let it challenge Rabbi Tarfon, since Rabbi Tarfon said that one recites both a first and an after-blessing. From the fact that the Gemara did not raise the challenge from Rabbi Tarfon against Rav Pappa, it must be that Rabbi Tarfon held that one recites only a first blessing and not an after-blessing. We have completed Keitzad Mevarchin.