Matthew 5:34

Ἐγὼ δὲ λέγω ὑμῖν μὴ ὀμόσαι ὅλως· μήτε ἐν τῷ οὐρανῷ ὅτι θρόνος ἐστὶ τοῦ Θεοῦ·

But I say to you, Do not swear at all; neither by heaven, because it is the throne of God,