He prohibited us - that we not deny obligations that we are indebted and deposits held by us. And that is His saying, "you shall not deny" (Leviticus 19:11); and it is explained that the verse is speaking about money. And the language of the Sifra (Sifra, Kedoshim, Section 2:3) is "Since it is stated, 'and denies it and swears falsely' (Leviticus 5:22), we have heard the punishment. From where [do we know] the prohibition? [Hence] we learn to say, 'you shall not deny.'" And you already know that one who denies a deposit [being held by him] is disqualified from testimony - even though he did not swear - since he transgressed the negative commandment, "you shall not deny." And the regulations of this commandment have already been explained in Tractate Shevuot. (See Parashat Kedoshim; Mishneh Torah, Oaths 1.)