Today Solomon presses on in his preaching against making false promises before God

Ecc 5:6  Don’t let your mouth make you sin. And don’t defend yourself by telling the Temple messenger that the promise you made was a mistake. That would make God angry, and he might wipe out everything you have achieved.

Ecc 5:7  Talk is cheap, like daydreams and other useless activities. Fear God instead.

Truer words were never spoken, talk is indeed cheap.  People can run their mouths all day long and have nothing to show for it.  Even Plato the Pagan philosopher was in agreement on this when he said “As empty vessels make the loudest sound, so they that have the least wit are the greatest blabbers”

While this is applicable in a day to day sense through our interactions with others, going back to what Solomon said, it is a far more dangerous offense to make false and empty promises to God.  

Jesus also had a very important insight on what comes out of our mouths and why it is best to keep them shut when He said in Matthew 15:11 “It is not what enters into the mouth that defiles the man, but what proceeds out of the mouth, this defiles the man.”

Our mouths are what get us into trouble, whether it is with others or in this case, with God, so best to sit back and observe rather than mouth off.