33 Πάλιν ἠκούσατε ὅτι ἐρρέθη τοῖς ἀρχαίοις· οὐκ ἐπιορκήσεις, ἀποδώσεις δὲ τῷ κυρίῳ τοὺς ὅρκους σου. 34 ἐγὼ δὲ λέγω ὑμῖν μὴ ὀμόσαι ὅλως· μήτε ἐν τῷ οὐρανῷ, ὅτι θρόνος ἐστὶν τοῦ θεοῦ, 35 μήτε ἐν τῇ γῇ, ὅτι ὑποπόδιόν ἐστιν τῶν ποδῶν αὐτοῦ, μήτε εἰς Ἱεροσόλυμα, ὅτι πόλις ἐστὶν τοῦ μεγάλου βασιλέως, 36 μήτε ἐν τῇ κεφαλῇ σου ὀμόσῃς, ὅτι οὐ δύνασαι μίαν τρίχα λευκὴν ποιῆσαι ἢ μέλαιναν. 37 ἔστω δὲ ὁ λόγος ὑμῶν ναὶ ναί, οὒ οὔ· τὸ δὲ περισσὸν τούτων ἐκ τοῦ πονηροῦ ἐστιν.
33 Again, you have heard that it was said to the ancients, “You [singular] will not break your oath, but you will fulfill your vows.” 34 But I am telling you all to not make oaths at all. Not by heaven, because it is the throne of God, 35 nor by the earth, because it is his footstool, nor for the sake of Jerusalem, because it is the city of the great king, 36 nor by your head shall you swear because you do not have power to make one hair white or black. 37 Instead, let your word be Yes or No. Anything more than this is from the evil one.
Two of the most important ideas to keep in mind when reading the Sermon on the Mount are that:
- Matthew wrote it because he thought Jesus really wanted us to put it into practice.
- There are exceptions to many of the commands that are simply assumed without elaboration. So the point is probably not merely that all oaths are bad (Jesus answered under oath in court in Matthew 26:63). There is likely to be something else going on.
There is some evidence that ancient persons were not future oriented in the same way that modern Americans are (note how often Paul cancelled his travel plans in his letters). In this way, it is possible that people would make lofty oaths to gain honor and trust in the present even though they had no intention to keeping their vows in the future. In fact, in 2 Corinthians, Paul notes that he wasn’t a man who broke oaths, but that his vacillation between visiting or not was not dishonesty but legitimate frustration with the Corinthians that kept him from visiting (2 Cor 1:16-24).
What Jesus seems to be saying is that grand gestures of fealty and integrity are unnecessary for God’s people. We simply need to say, ‘Yes’ or ‘No.’ Oaths taken for honor’s sake in the Old Testament never turned out well. Jesus even tells people to consider whether they will follow him and to weigh the options carefully (Luke 14:26-35). This is a message that is greatly needed in our present culture because lofty promises are made by politicians and millennial types often never show up to things they claimed they would intend. In a real way, Jesus’ teaching here appears to be moving integrity to the locus of personal consistency rather than the external locus of group rapport.
There is no reason for the phrase, “μήτε εἰς Ἱεροσόλυμα” to be translated “nor by Jerusalem.” It carries the force, “nor for the sake of Jerusalem.” In other words, don’t even take oaths for the city. I’ll have to look more deeply into this expression, but my instinct is that it is related to political zealotry, perhaps oaths to attack Rome when the moment is right. But the point is not the oaths, (which are prohibited with the infinitive, not the imperative), but the point is that that Jesus commands us to simply say yes or no and to do what we say we’ll do.
 Kurt Aland et al., Novum Testamentum Graece, 28th Edition. (Stuttgart: Deutsche Bibelgesellschaft, 2012), Mt 5:33–37.