Arcing Commentary -
The main idea of the passage is that we ought not to swear, but to speak truth. Those two statements form our main (+/-) of the passage (v.34-36 and v.37).
Within v.34-36, Jesus gives 4 examples of bad oaths. Each item (heaven, earth, Jerusalem, hair) is followed by reasons we ought not to swear by them.
In contrast to all these false oaths, there is the + value of simply saying, "yes yes" or "no, no."
I made v.37b a ground for 37a even though there wasn't a connecting "for" or "because" because the statements seemed to fit well. Speak only "yes" or "no"because anything more comes from evil. I would not arc it as a "series" even though there is a connecting word (de) because they are talking about two different topics, there's more than just a "don't swear and anything more comes from evil."
Jesus continues to rebuke false interpretations of the Law, and this one I think refers to the habit of the Pharisees to say, "If you swear by the temple, you are bound but if you don't swear by the temple, you are not." A similar idea (maybe the same?) is found in Matt. 23's 7 woes -
16 “Woe to you, blind guides, who say, ‘If anyone swears by the temple, it is nothing, but if anyone swears by the gold of the temple, he is bound by his oath.’ 17 You blind fools! For which is greater, the gold or the temple that has made the gold sacred? 18 And you say, ‘If anyone swears by the altar, it is nothing, but if anyone swears by the gift that is on the altar, he is bound by his oath.’ 19 You blind men! For which is greater, the gift or the altar that makes the gift sacred? 20 So whoever swears by the altar swears by it and by everything on it. 21 And whoever swears by the temple swears by it and by him who dwells in it. 22 And whoever swears by heaven swears by the throne of God and by him who sits upon it.
Woe! How do we think that swearing on a temple does anything? It is God who owns these things. How do we think we can swear by our head? We cannot make a hair white or black (as I have recently realized). Instead, we ought to simply speak truth, say "yes" or "no" and then do it.
This also rebukes my need to say, "well, I'll really do it this time, I swear." I ought to be living lives of such integrity that when I say, "I'll do it," people will believe me. Do I keep my appointments or am I perpetually 5-15 minutes late?