'Knows' in the Bible

He said, "While the child was yet alive, I fasted and wept; for I said, 'Who knows whether Yahweh will not be gracious to me, that the child may live?'

Joab fell to the ground on his face, and did obeisance, and blessed the king. Joab said, "Today your servant knows that I have found favor in your sight, my lord, king, in that the king has performed the request of his servant."

Even he who is valiant, whose heart is as the heart of a lion, will utterly melt; for all Israel knows that your father is a mighty man, and those who are with him are valiant men.

For your servant knows that I have sinned. Therefore, behold, I have come this day the first of all the house of Joseph to go down to meet my lord the king."