The Rambam paskens (Bikkurim 10:14) that if partners own a flock of 5 sheep b’shutfus, they are patur from reishis hageiz, but if the flock contains 10 sheep, the two partners are chayavim. The Minchas Chinuch writes that the Rambam paskens like R’ Ilayei, that shutafim are pturim from reishis hageiz - 5 sheep owned by two partners means each one individually lacks the necessary shiur to fulfill the mitzvah. Where there are enough sheep so each partner independently can be said to own a sufficient shiur to be chayav (e.g. 10 sheep), the Rambam ignores the ptur of shutfus and writes that each partner is indeed chayav. R’ Chaim Brisker disagrees, and points out that the gemara applies the machlokes R”I and the Chachamim to terumah, where there is no minimum shiur required. No matter what quantity of tevel is owned it is chayav in terumah, yet R' Ilayei still holds shutafim would be exempt! One is forced to say that the exemption of shutfus is based on it being a qualitatively different type of ownership and excluded from the mitzvah, not simply based on each partner's share being less than the necessary shiur to be chayav. Even if there are 10 sheep in a flock, R’ Ilayei would hold shutafim are pturim, while the Chachaim, like whom the Rambam paskens, hold the shutafim are chayav. However, according to this approach, we are left with a question on the Rambam. By challah (to come back to another topic of late!) the Rambam paskens (Bikkurim 6:4) shutafim are chayavim if the total amount of dough owned is 43 1/5 beitzim, the same shiur that applies to an individual owner. By reishis hageiz, however, the Rambam paskens a flock of 5 sheep is not chayav – the chiyuv applies only if there are 5 sheep per owner. If 43 1/5 beitzim in total owned by shutafim is chayav in challah, why should 5 sheep in total not be chayav in reishis hageiz?
This is a warm up to get the gavra/cheftza juices flowing… if you’ve heard a few R’ Chaim’s, you should be able to get this one.