18 For the one who serves Christ in this way is pleasing to God and approved by people. 19 So then, let us pursue what makes for peace and for building up one another. 20 Do not destroy the work of God for the sake of food. For although all things are clean, it is wrong to cause anyone to stumble by what you eat. 21 It is good not to eat meat or drink wine or to do anything that causes your brother to stumble. 22 The faith you have, keep to yourself before God. Blessed is the one who does not judge himself by what he approves. 23 But the man who doubts is condemned if he eats, because he does not do so from faith, and whatever is not from faith is sin.

The Gemara asks: But is there a prohibition of: He shall not profane, by rabbinic law? The Gemara answers: Yes, and it is taught in a baraita: With regard to matters that are permitted, but others are accustomed to observe a prohibition with regard to them, you may not permit these matters before those people, as it is stated: “He shall not profane his word” (Numbers 30:3). If they contravene their custom they are in violation of the prohibition: He shall not profane his word, by rabbinic law, as that is similar to violating a vow. The Gemara attempts again to raise a difficulty with regard to Rav Yehuda’s opinion. We learned in a mishna (57a) that if a man said to his wife: Deriving benefit from me until Passover is konam for you if you go to your father’s house until the following festival of Sukkot, then, if she went to her father’s house before Passover, she is prohibited from deriving benefit from him until Passover, as she violated the condition, thereby enabling the vow to take effect.