At the core of the concept that thoughts shouldn't be blurted aloud without consideration is that words can cause such damage
It is why the Apostle Paul admonished believers to renew their mind and transform themselves so they would
speak what's right and good in agreement with God's Word...
Romans 12:2 And do not be conformed to this world, but be transformed by the renewing of your mind, that you may prove what is that good and acceptable and perfect will of God.
Chronicled in the four gospels, Jesus cast out demons and healed the multitudes by the spoken word according to God's will (1John 5:14-15). He rebuked "the tempter" in the wilderness –
Matthew 4:4 But He answered and said, "It is written, 'Man shall not live by bread alone, but by every word that proceeds from the mouth of God.' "
Scripture states that speech can invoke great things or create chaos. Beginning with the very first book of the Bible, God creates through speaking:
Genesis 1:3 And God said, Let there be light: and there was light. (Speaking manifestations: Joshua 10:12-13, Job 22:28, Mark 5:8, Mark 11:23, Acts 2:5-11, etc.)
At the core of the concept that thoughts shouldn't be blurted aloud without consideration is that words can cause such damage that individuals may be hurt and even nations can be destroyed as a result...