What does 2 Corinthians 1:22 mean?

This is part of a response to accusations that Paul has shown lack of commitment. This is aimed at his changing of travel plans to come and visit the believers in Corinth. Paul is declaring something the Corinthians would surely agree with: God, he has said, is the one who established both him and the Corinthians in Christ. God is the one who has anointed them all with the Holy Spirit.

Now Paul adds that in giving them the Spirit in their hearts, God has put His seal on them. He has given the Holy Spirit to each believer as a guarantee or deposit or down payment. In Paul's day, a seal was a mark stamped in wax that showed ownership. Those sealed with the Holy Spirit belong to God, and they belong to God forever. The Spirit is a guarantee that we will remain in God's possession throughout this life and into eternity. God's Spirit in our hearts serves as evidence that Christians are secure in God's family.

So, then, all who are established in Christ by God and anointed with the seal of God's Holy Spirit by God are guaranteed by God to spend eternity with God.