God wants us to let out yes be yes and our no be no. I'm sure there is more history behind what these oaths referred to that I wish I knew, but from reading it straight at value, what I read is that God doesn't want what we say to be backed up by an oath.
He doesn't want us to say "I swear by God I will do this!" Or "I swear by my hair that I will do it."
When we say yes we will do it, we do it. When we say no we won't do it, don't do it.
A side observation, I think it's a cool observation about heaven being God's throne and earth being His footstool and Jerusalem being the city for the Great King. Great observation on how big God is and the description of what heaven and earth - picture of His kingdom :)
I really need a good commentary recommendation, because reading through this without the historical background can be a little bit blank, I think solid rock has spoiled me in the way I get taught with a history lesson. I really wish I knew what these things referred to because it would make this time that much richer...
Don't swear in making promises to one another. Let my word be my word.