Matthew 5:37

Ἒστω δὲ ὁ λόγος ὑμῶν ναὶ ναί οὒ οὔ· τὸ δὲ περισσὸν τούτων ἐκ τοῦ πονηροῦ ἐστιν.

But in your speech let ‘Yes’ be ‘Yes’, ‘No’ be ‘No’; and anything beyond these is of the evil one.