'Assurance' in the Bible

For we are become companions of the Christ if indeed we hold the beginning of the assurance firm to the end;

But we desire earnestly that each one of you shew the same diligence to the full assurance of hope unto the end;

let us approach with a true heart, in full assurance of faith, sprinkled as to our hearts from a wicked conscience, and washed as to our body with pure water.