'Confirmation' in the Bible

For men verily swear by the greater: and an oath for confirmation is to them an end of all strife.

And the Holy Spirit also adds His testimony to us [in confirmation of this]; for after having said,

Now faith is the assurance (title deed, confirmation) of things hoped for (divinely guaranteed), and the evidence of things not seen [the conviction of their reality—faith comprehends as fact what cannot be experienced by the physical senses].