'Assurance' in the Bible

so that their hearts may be encouraged, united in love and into all the wealth of the full assurance of insight into the knowledge of the mystery of God, Christ,

And we desire each one of you to demonstrate the same diligence for the full assurance of [your] hope until the end,

let us approach with a true heart in the full assurance of faith, our hearts sprinkled [clean] from an evil conscience and our bodies washed with pure water.