'Truly' in the Bible

But David vowed again, saying “Your father certainly knows that I have found favor in your sight, and he has said, ‘Do not let Jonathan know this, or he will be worried.’ But truly as the Lord lives and as your soul lives, there is hardly a step between me and death.”

David answered the priest, “Be assured that women have been kept from us in these three days since I set out, and the bodies of the young men were consecrated (ceremonially clean), although it was an ordinary (unconsecrated) journey; so how much more will their vessels be holy today?”