What is a kosher condition? TB Nedarim 11

Trying to figure out who is the author of the Mishnah on daf TB Nedarim 11, we learn how to make a kosher condition. The Mishnah begins “If one says to another: That which I eat of yours shall be considered laḥullin, it is interpreted as though he said: La ḥullin, not non-sacred, and the food is thereby forbidden to him.” (Sefaria.org translation) The person making that sentence uses a negative phrase to infer something positive, i.e. not non-sacred meaning sacred. This can’t be Rabbi Meir’s position; consequently, he can’t be the author of our Mishnah.

“Whose opinion is expressed in the mishna? If you say it is that of Rabbi Meir, he does not hold that from a negative statement you can infer a positive statement. As we learned in a mishna: Rabbi Meir says that any condition that is not like the condition of the sons of the tribe of Gad and the sons of the tribe of Reuben, when Moses gave them land on the eastern bank of the Jordan River (see Numbers 32:29–30), is not a valid condition. Moses phrased the agreement as a double condition, stating that if they would join the other tribes in battle they would receive their inheritance on the eastern bank of the Jordan River, and if not, they would not receive that territory. Because Rabbi Meir holds that only a condition expressed in this manner is valid, it is clear that he holds that one may not infer a negative statement from a positive one or vice versa.” (Sefaria.org translation)

Here’s the back story that teaches that a double condition, stating both the positive and the negative, must be used to be binding. The children of Israel are poised to enter the land of Israel by crossing over the Jordan River. The tribes of Gad, Reuvan, and half of Menashe want to remain on the eastern bank of the Jordan River because it was cattle country and they had a lot of cattle. Moses initially was angry at them thinking they were refusing to obey God’s commandment to enter the land of Israel as did the generation of the spies. (Because of the sin of the generation spies, the Israelites were forced to wander in the wilderness for 40 years.) The tribes of Gad, Reuvan, and half of Menashe reassured Moses they would join their brothers and help them conquer the land of Israel before settling down on the eastern bank of the Jordan River.

“Then they stepped up to him and said, “We will build here sheepfolds for our flocks and towns for our children. And we will hasten as shock-troops in the van of the Israelites until we have established them in their home, while our children stay in the fortified towns because of the inhabitants of the land. We will not return to our homes until the Israelites—every one of them—are in possession of their portion. But we will not have a share with them in the territory beyond the Jordan, for we have received our share on the east side of the Jordan.” (Numbers 32:16-19)

Notice that Moses formulates the condition both in the positive and in the negative so there can be no misunderstanding of the terms the condition. “Moses said to them, “If you do this, if you go to battle as shock-troops, at the instance of God, and every shock-fighter among you crosses the Jordan, at the instance of God, until [God] has personally dispossessed the enemies, and the land has been subdued, at the instance of God, and then you return—you shall be clear before God and before Israel; and this land shall be your holding under God. If you do not do so, you will have sinned against God; and know that your sin will overtake you. Build towns for your children and sheepfolds for your flocks, but do what you have promised.” (Numbers 32:20-24)

All conditions have to be like the conditions of the tribes of Gad and Reuvan and if they don’t follow this format they are not considered conditions at all (with just a few exceptions). The condition has to the following four elements: 1, the condition must be double (תנאי כפול), meaning both the positive and the negative are expressed; 2, the positive formulation comes before the negative; 3, the condition must proceed the action itself; 4 the condition must be something that is possible to fulfill. (Shulkhan Arukh, Even Ha’ezer you 38:2)