And do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.
In verse 30, Paul adds to the characteristics of the new man, that we should not grieve the Holy Spirit of God.
The fact that the Holy Spirit can be grieved is one of the evidences of the fact that the Holy Spirit is a person, not a force or influence.
Grieve means to pain, grieve or vex. Sometimes it is translated made sorry, or sad. The Christian should not behave in ways or have thought patterns that grieve or sadden or trouble the Holy Spirit. We learn and know how the Holy Spirit thinks by reading and meditating on the Scriptures. The more we are in the Word, the more we will be able to recognize those attitudes in us which are likely to cause grief to the Holy Spirit. Once identified, we should apply all of the biblical principles we know to avoid those behaviors and thought-patterns. It is a process of renewing the mind.
Paul goes on to tell us that it is the Holy Spirit who has sealed us for the day of redemption. There is coming a day when we will be fully redeemed. There is the fact of our current redemption as well, but in the day of redemption, we will be fully redeemed not only from the power and guilt of sin, but of the very presence of sin as well.
The Holy Spirit seals us to protect us until that day so that it is impossible for us to fall away or be snatched out of the Father’s hand (John 10:28-29). Paul had already written the Ephesians about this in 1:13 telling us that we “were sealed with the Holy Spirit of promise.”
In 1 Corinthians 1: 21-22 we read: “And it is God who establishes us with you in Christ, and has anointed us, and who has also put his seal on us and given us his Spirit in our hearts as a guarantee.”
Guarantee means down payment. When you put a down payment on a car, the idea is that if you change your mind and decide not to go through with the deal, the seller gets to keep the down payment. There is no way that, having given us the Holy Spirit as a down payment, God is going to renege (back out) of his promise.