'Certain' in the Bible

And he said to them, Take me up and put me into the sea, and the sea will become calm for you: for I am certain that because of me this great storm has come on you.

And he made prayer to the Lord and said, O Lord, is this not what I said when I was still in my country? This is why I took care to go in flight to Tarshish: for I was certain that you were a loving God, full of pity, slow to be angry and great in mercy, and ready to be turned from your purpose of evil.