The Greek that is translated as “Let your word be ‘Yes, Yes’, or ‘No, No'” or similar in English is translated in Enga as “When you say that you will do something, just say that you will do it. When you say that you will not do something, just say that you will not do it.”

Adam Boyd (on his blog) explains: “In Enga, it is even more complex because there is no word for ‘Yes’; there is only a word for ‘No.’ So, to say ‘Yes,’ Engans restate the action of the verb in the affirmative. For example, if I were to ask Martha in Enga, ‘Did you go to the store?’ she would reply, ‘I went.’ If she wanted to reply, ‘No,’ she could either say ‘I didn’t go,’ or ‘No, I didn’t go.’ Engans also have shortcuts for the word ‘Yes.’ One shortcut is to utter something in between a grunt and a sigh; the other is to raise one’s eyebrows. I still have trouble with the raising of the eyebrows. Often I find myself repeating a question over and over again when I forget that raised eyebrows means ‘Yes.’ Instead, I think that people have just misunderstood me or perhaps did not hear me.

“This makes things difficult when translating Jesus’ words in Matthew 5:37, ‘Let your word be ‘Yes, yes,’ or ‘No, no.’’ This is further complicated by the fact that the context of Jesus’ words in Matthew 5:37 is his command not to swear any oaths at all. Not only does Enga have no word for ‘yes,’ but Enga also has no proper word for ‘oath.’ At first, we translated the idea of swearing an oath as ‘say that you are speaking very truly,’ but we soon discovered that such a translation would not work as Jesus himself frequently says, ‘Truly, truly, I say to you.’ So after much consideration, we translated ‘swear an oath’ as ‘say the name of something and then say very truly that you will do something.’ We found this to be an acceptable translation because swearing an oath usually requires invoking the name of God or something else (such as the saying, ‘I swear on my mother’s grave’). Having solved the problem of translating ‘swear an oath,’ we were then able to translate Jesus’ words, ‘Let your word be ‘Yes, yes,’ or ‘No, no,” as ‘When you say that you will do something, just say that you will do it. When you say that you will not do something, just say that you will not do it.'”

See also swear / vow.