Question: When must one swear to one’s friend? Similarly, is there any prohibition in what many people tell their friends “I swear to you” about nonsense?
Answer: The primary aspect of a Torah-prescribed oath is that one must swear to another in Bet Din (rabbinical court) under certain circumstances, for instance, if Reuven claims that Shimon owes his one-thousand dollars and Shimon claims that he only owes five-hundred, the Torah obligates Shimon (who is not claiming that the entire claim is false; rather, he is admitting that it is only partially true) swear in front of the Bet Din that he only owes the five-hundred he claims he owes and in doing so, he exempts himself from paying the remainder of the claim against him. This is the oath of “one who admits partially” derived by our Sages in Masechet Shevuot. There are other forms of oaths, some Torah-prescribed, some by the law of the Mishnah, and others based on rabbinic law derived by the Sages of the Talmud and others who followed.
One who became obligated to swear in Bet Din would do so in the name of Hashem, i.e. the individual would say, “I hereby swear in the name of Hashem, G-d of Israel” or “I hereby swear in the name of the Merciful/Gracious One that I only owe my friend five-hundred dollars.” He would then pay the five-hundred dollars and would be exempt from the remainder of the claim.
The basic meaning behind an oath is that just as Hashem is true, so too, the idea that I am claiming is also true. Thus, if one lies under such an oath, one is hereby desecrating the great and holy name of Hashem and his sin is too great to bear.
When uttering the oath, one is given a Sefer Torah to hold in order to threaten him to tell the truth. It was customary that before the oath was taken, a coffin would be brought into the Bet Din and the candles in the courtroom would be dimmed. All this was done in order to bring the litigant to a point of fear and submission so that he would not, G-d-forbid, transgress the sin of swearing falsely.
The judges would tell the individual, “Know that when Hashem uttered the commandment of ‘You shall not bear the name of Hashem, your G-d, in vain’ at Mount Sinai, the entire world shook. Regarding any of the other prohibitions in the Torah, only the sinner is punished whereas with regards to the sin of swearing falsely, the sinner and his family are punished. Even more so, the entire world is punished as well. Furthermore, regarding any other prohibition in the Torah, if one has merits, they will protect the individual so that he is not punished immediately in hopes that he may repent in the future. On the other hand, regarding the sin of swearing falsely, one is punished immediately.” Similarly, the judges tell the plaintiff who requires the defendant to swear, “Be careful not to cause your friend to swear, for when one does so, this causes one do lose one’s assets and become poor.” The Gemara and its commentaries (Shevuot 39a) speak lengthily about the dangers of swearing falsely and why seemingly innocent people, such as the individual’s family and the rest of the world, are punished as well.
Before taking the oath, the judges tell the individual, “See here that we are not making you swear according to your own understanding (of the truth); rather, this is being done according to the understanding of (the truth according to) Hashem and that of the Bet Din.” The Gemara (Shevuot 29a) explains that the reason they did this is because once, an incident occurred in the Bet Din of Rava whereby Reuven claimed that Shimon owed him a sum of money and Shimon denied it. Rava obligated Shimon to swear and before he did, he went home to fetch a cane. Before uttering the oath, Shimon asked Reuven to hold the cane so that he could take the Sefer Torah. He then proceeded to swear. Reuven became so infuriated that Shimon would lie so blatantly that he took the cane and threw it on the ground forcefully, causing it to shatter. When that happened, many coins spilled all over the Bet Din’s floor. This means that Shimon did indeed swear truthfully because he did return the sum of money Reuven claimed he owed him, however, according to the understanding of the Bet Din, this was a false oath because they did not understand his deceitful intentions. This is why they enacted that one must swear truthfully according to the understanding of the Bet Din in which case these kinds of tricks will all be worthless.
Rashi writes that in later generations, swearing in the name of Hashem was abolished because the punishment for doing so falsely is so grave. It has therefore become customary to make one swear in a roundabout manner by the Bet Din proclaiming, “So-and-so is hereby cursed if he owes the plaintiff more than he admits he is” and the defendant answers “Amen”. Thus, although this halachically constitutes an oath, nevertheless, this is not as serious as an actual oath in the name of Hashem. Maran Ha’Shulchan Aruch (Choshen Mishpat, Chapter 87) quotes this opinion as “Some say”.
In the following Halacha we shall discuss the custom that many people have to tell their friends “I swear to you” in order to validate their words.