הלכה על סנהדרין 113:25

It laws: For example, that which our Rabbis, may their memory be blessed, said (Sanhedrin 57a) how much would the theft be that obligates the robber in repayment? Any theft that is worth a small coin (perutah). But less than that is not in the category of repayment, even though he has transgressed a Torah prohibition. And as we shall write at length in the negative commandment of "You shall not rob" (Sefer HaChinukh, 20, 29), [it is] because Israelites are the children of Avraham, Yitschak and Yaakov - generous men, the children of generous men. And it is a well-known thing that that even a poor Israelite will pardon less than the worth of a perutah that was stolen from him, and he will not want to seek it at all. And therefore, they, may their memory be blessed, said (Bava Kamma 105a) that one who robs three bundles, worth three perutah at the time of the theft, and they depreciate in the hand of the robber and became worth two perutah - even though he returned two - he is obligated to return the third; since we judge according to the time of the robbery, and [the] third was already worth a perutah at that time. [If] he stole two that are worth one perutah [together] and he returned one, there is robbery here [but] there is not repayment here.