2 Corinthians 1:18-22
18 But as surely as God is faithful, our message to you is not “Yes†and “No.†19 For the Son of God, Jesus Christ, who was preached among you by us—by me and Silas[a] and Timothy—was not “Yes†and “No,†but in him it has always been “Yes.†20 For no matter how many promises God has made, they are “Yes†in Christ. And so through him the “Amen†is spoken by us to the glory of God. 21 Now it is God who makes both us and you stand firm in Christ. He anointed us, 22 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
13 And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit, 14 who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory.