Who also has sealed us and given us the Spirit in our hearts as a guarantee.
The apostle Paul wanted the Corinthians to know that the message of Christ and God’s promises were not “Yes and No” (2 Corinthians 1:19), contradictory or wishy-washy. God is faithful and positive, and He has sealed true Christians and given them the Holy Spirit. “Sealing indicates ownership and security” (Nelson’s NKJV Study Bible, note on 2 Corinthians 1:21-22).
The gift of the Holy Spirit is like a down payment on the future blessings and eternal life that God offers to those who repent, are baptized, receive the Holy Spirit and commit to living a life of obedience that is pleasing to God.
For more about the gift of the Holy Spirit, see “How Do You Know You Have the Holy Spirit?”