The gemara asks why do I need a secondary pasuk that teaches that regel is related to the expression v'shilach (meshalchei regel hashor), because even without that it would be obvious that v'shilach refers to regel, since keren and shain are already known.
But how would I know that there is such a concept of regel at all? It's true that v'shilach can't be coming to teach keren or shain, but without the other pasuk, why would I assume a new category of nezek just from the word v'shilach?
Yaron Barach, Brooklyn NY
Many commentaries indeed ask why we would not say that the Pasuk is referring to something else, such as a Toldah of Shen or a Toldah of Regel (first comment in Shitah Mekubetzes here) or a case of Keren in which the Rabbanan say one is not liable to pay (Rebbi Akiva Eiger). They all give answers why these options are not liable, leaving Regel as the only viable option. The Pnei Yehoshua (his first comment on the Amud) understands that this terminology of the Pasuk certainly indicates Regel.
All the best,
Yaakov Montrose