'Guard' in the Bible

For the lips of a priest should guard knowledge, and people should seek instruction from his mouth, because he is the messenger of the Lord of Hosts.

Did he not make them one? And the vestige of the spirit remains in him. And why did he make them one? He was seeking godly offspring. So guard yourselves in your spirit, and don't be unfaithful to the wife of your youth.

"Indeed, the LORD God of Israel says that he hates divorce, along with the one who conceals his violence by outward appearances," says the LORD of the Heavenly Armies. "So guard yourselves carefully, and don't be unfaithful."