Matthew 5:37
Let what you say be simply Yes or No; anything more than this comes from evil. The positive alternative to oath-taking is the simple yes or no of trustworthy speech — the person whose word is always reliable has no need of oaths to validate particular statements. Anything more than this comes from evil — the need for oaths arises from the fact that ordinary speech cannot be trusted, that the culture of deception has made oath-enforcement necessary. James 5:12 repeats the teaching almost verbatim: let your yes be yes and your no be no. The community that practices consistent truthfulness renders the oath-system unnecessary because every statement carries the weight of integrity.