הלכה על שבועות 98:20

That is that He commanded us about the law of the [paid guardian] and the renter - since the law of the two of them is the same, as they explained and said (Shevuot 49b), "There are three laws for four [categories of] guardians." And that is His, may He be exalted, saying, "When a man gives to his fellow, etc." (Exodus 22:9). And all the regulations of this commandment have already been explained in Chapter 6 and 8 of [Bava] Kamma, 8 of [Bava] Metzia and 8 of Shevuot. (See Parashat Mishpatim; Mishneh Torah, Borrowing and Deposit 1-5.)