Last week’s Parsha alluded to the concept of מודה במקצת, admitting partially to an accusation. It is also an interesting observation regarding human nature.
The Torah emphasizes the words, כי הוא זה, which is defined as a type of confession. The case refers to the repayment of a loan.
If one is asked to pay back money that he borrowed, and the borrower claims that he never borrowed anything, he is exempt from payment. The burden of proof is on the lender.
However, if the borrower admits that he did borrow money, but not the entire amount claimed, he must make a biblical oath. He holds on to a Torah scroll and swears in G-d’s holy name the amount he claims that he owes. He pays only that amount.
The rationale of the Rabbis is that a Jew would not dare deny entirely a loan he would receive. However, he could deny part of the loan. This is their perception of human nature. This is the case of מודה במקצת.