2 Corinthians 1:22

He anointed us, set His seal of ownership on us, and put His Spirit in our hearts as a deposit, guaranteeing what is to come.

Ephesians 1:13-14

In Him, you also, after listening to the message of truth, the gospel of your salvation--having also believed, you were sealed in Him with the Holy Spirit of promise, Who is given as a pledge of our inheritance, with a view to the redemption of God's own possession, to the praise of His glory.