15 And with this confidence I intended to come to you first so that you would get a second opportunity to see us, 16 and through your help to go on into Macedonia and then from Macedonia to come back to you and be helped on our way into Judea by you. 17 Therefore when I was planning to do this, I did not do so without thinking about what I was doing, did I? Or do I make my plans according to mere human standards so that I would be saying both “Yes, yes” and “No, no” at the same time? 18 But as God is faithful, our message to you is not “Yes” and “No.”

The Gemara raises an objection: Rabbi Yosei, son of Rabbi Yehuda, says: What is the meaning when the verse states: “A just ephah, and a just hin, shall you have” (Leviticus 19:36)? But wasn’t a hin included in an ephah? Why is it necessary to state both? Rather, this is an allusion that serves to say to you that your yes [hen] should be just, and your no should be just. Apparently, it is a mitzva for one to fulfill his promises. Abaye says: That verse means that one should not say one matter with his mouth and think one other matter in his heart. It is prohibited for one to make a commitment that he has no intention of fulfilling. Rav Kahana made his commitment in good faith and reneged due to changed circumstances. That is not prohibited.