Shiur Supplement - Daf 5a
A. U-le-man de-amar heilakh patur... u-me'arot [lines 1-5] BACKGROUND: The gemara (Shevu'ot 42b-43a) learns out from the passuk (Shemot 22:6): "If a man gives to his friend money or vessels to guard..." that the Torah requires one to swear regarding only movable items which have an inherent value. Thus, one is exempt from taking a shevu'a regarding land. (For example, should the defendant admit partially to claim for land, he would not have to take the shevu'a of a modeh be-miktzat.)
As we have seen in the previous daf, admitting that one owes land is tantamount to saying "heilakh". The gemara questions why we need a special passuk to tell us that there is no shevu'a when we are dealing with land - the defendant is exempt as it is a case of heilakh! [This question relates only to R. Sheshet. It is obvious why R. Chiya, who mandates a shevu'a in the case of heilakh, requires the passuk to exempt land.]
The gemara answers that we require the passuk to exempt one from a shevu'a in the following case: The defendant damaged the land of the plaintiff by digging a cistern etc. Although, he admits guilt, he acknowledges having caused less damage than he is being sued for (modeh be-miktzat). This is not a case of heilakh, but the Torah, nonetheless, exempts him from swearing.