10 As an example of suffering and patience, brothers and sisters, take the prophets who spoke in the Lord’s name. 11 Think of how we regard as blessed those who have endured. You have heard of Job’s endurance and you have seen the Lord’s purpose, that the Lord is full of compassion and mercy. 12 And above all, my brothers and sisters, do not swear, either by heaven or by earth or by any other oath. But let your “Yes” be yes and your “No” be no, so that you may not fall into judgment. 13 Is anyone among you suffering? He should pray. Is anyone in good spirits? He should sing praises. 14 Is anyone among you ill? He should summon the elders of the church, and they should pray for him and anoint him with olive oil in the name of the Lord.
Bava Metzia 49aBabylonian Talmud
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.
Notes and References
"... In Rabbinic literature, as well, the words 'yes, yes' and 'no, no' are taken to imply an oath. Thus in tractate Shebuot, Raba explains that 'yes' alone is not an oath: 'But that is on condition that he said no, no twice or yes, yes twice ... and, then, since 'no' has to be said twice to mean an oath, so, too, yes must be said twice to mean an oath' ..."
Welborn, L. L. Politics and Rhetoric in the Corinthian Epistles (pp. 161-163) Mercer University Press, 1997