'Know' in the Bible

But we know that the law is good, if a man uses it lawfully,

(but if a man doesn't know how to rule his own house, how will he take care of the assembly of God?)

but if I wait long, that you may know how men ought to behave themselves in the house of God, which is the assembly of the living God, the pillar and ground of the truth.

forbidding marriage and commanding to abstain from foods which God created to be received with thanksgiving by those who believe and know the truth.