'Guarantee' in the Bible

And He will also confirm you to the end [keeping you strong and free of any accusation, so that you will be] blameless and beyond reproach in the day [of the return] of our Lord Jesus Christ.

it is He who has also put His seal on us [that is, He has appropriated us and certified us as His] and has given us the [Holy] Spirit in our hearts as a pledge [like a security deposit to guarantee the fulfillment of His promise of eternal life].

Now He who has made us and prepared us for this very purpose is God, who gave us the [Holy] Spirit as a pledge [a guarantee, a down payment on the fulfillment of His promise].

The Spirit is the guarantee [the first installment, the pledge, a foretaste] of our inheritance until the redemption of God’s own [purchased] possession [His believers], to the praise of His glory.

And so [because of the oath’s greater strength and force] Jesus has become the certain guarantee of a better covenant [a more excellent and more advantageous agreement; one that will never be replaced or annulled].