The fear of taking an oath prevents lying TB Baba Metzia 5

The rabbis were reluctant to impose an oath which necessarily included God’s name for fear that the person would be swearing falsely and using God’s name in vain. Almost from the very beginning of our massekhet through today’s daf TB Baba Metzia 5, the Gemara has been analyzing whether the court should imposes an oath upon the person who admits to part of the claim (modeh bemiyzat-מוֹדֶה מִקְצָת) or not.

The today’s daf explains why in the case of the Mishna an oath is required and then asks the very good question. The Mishnah states: “If two people came to court holding a garment, and this one, the first litigant, says: I found it, and that one, the second litigant, says: I found it; this one says: All of it is mine, and that one says: All of it is mine; how does the court adjudicate this case? This one takes an oath that he does not have ownership of less than half of it, and that one takes an oath that he does not have ownership of less than half of it, and they divide it.” (daf 2a, Sefaria.org translation)  

The oath is required to prevent people taking advantage of the above scenario. “The Gemara questions the requirement that the litigants take an oath at all: But since this one is standing with half the item in his grasp and that one is standing with half the item in his grasp, and each party ultimately receives what is in his grasp, why is this oath necessary? Rabbi Yoḥanan says: This oath is an ordinance instituted by the Sages so that everyone will not go and seize the garment of another and say: It is mine.” (Sefaria.org translation)

Why should we believe that a thief would swear truthfully? “The Gemara asks: But let us say that since he is suspect with regard to financial dishonesty, i.e., stealing another’s property and lying in court that it belongs to him, he is also suspect with regard to taking an oath, and his oath cannot be accepted.” (Sefaria.org translation) The Gemara holds the supposition that people are willing to lie about money but not willing to swear an oath falsely. Tosefot ד"ה דַּחֲשִׁיד אַמָּמוֹנָא חֲשִׁיד אַשְּׁבוּעָתָא explains the underlying reason why people are unwilling to swear an oath falsely. Swearing falsely under oath is a very serious sin. The Gemara in TB Shavuot 39a teaches “Before he takes the oath, the judges say to him: Be aware that the entire world trembled when the Holy One, Blessed be He, said at Mount Sinai: “You shall not take the name of the Lord, your God, in vain, for the Lord will not hold guiltless one who takes His name in vain” (Exodus 20:7).” (Sefaria.org translation) Taking an oath is awesome.

One commentator explained the qualitative difference between taking God’s name in vain and all other transgressions. In all other transgressions when a person truly repents, he is forgiven and God doesn’t punish them. This is not the case in taking the Lord’s name in vain based on a close reading of this verse: “You shall not swear falsely by the name of your God יהוה; for יהוה will not clear one who swears falsely by God’s name.” (bold font for emphasis) Even when the person repents, God will exact some punishment.

Although the Torah holds that a thief may swear an oath, the rabbis did not permit such a person to take an oath based on human nature. Unscrupulous people have no compulsion to tell the truth even under oath.