- We are God's possession (v. 11, 14)
- The Holy Spirit has sealed us (v. 13)
- The Holy Spirit fulfills God's promise to save us (v. 13)
- The Holy Spirit guarantees our inheritance (v. 14)
What Paul is saying is that the experience of the Holy Spirit which we have in this world is a foretaste of the blessedness of heaven; and it is the guarantee that some day we will enter into full possession of the blessedness of God. The highest experiences of Christian peace and joy which this world can afford are only faint foretastes of the joy into which we will one day enter. It is as if God had given us enough to whet our appetites for more and enough to make us certain that some day he will give us all.
And some final help from Paul in Phillipians 1:6 (ESV):
I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ.
Listen to the message on eternal security here.