Question 36: What do we believe about the Holy Spirit?
Answer: That he is God, coeternal with the Father and the Son, and that God grants him irrevocably to all who believe.
The word “irrevocably” in the catechism answer indicates that, once God has given the gift of his Spirit to indwell you, that gift will never be taken away. The Holy Spirit marks believers in Christ indelibly as children of God, who will never be snatched away from him.
Whenever a person makes a big purchase and can’t pay for it all at once, he often makes a down payment, or a first installment on the whole price. Sometimes this may be called an earnest, a pledge, or a guarantee of more money to come. It represents a commitment from the buyer to pay off the rest of the price over time. Unfortunately, not all buyers end up being faithful to their purchase intentions over time, either because they end up lacking the resources or because they don’t make it a priority to keep their commitments. In God’s case, neither of these things is true: he never lacks resources, and he is always true to his commitments.
Therefore, when the Bible speaks of the gift of the Holy Spirit as a “guarantee of our inheritance” (Eph. 1:14), it is an indication that, once God has given the gift of his Spirit to indwell you, he will certainly not fail to give you the full inheritance of salvation in the age to come. The Holy Spirit is the first taste of the coming kingdom, which God will bring to his children without fail.
Suggested passage for personal or family reading: Ephesians 1:3-14. Do you see all three Persons of the Trinity in this passage? What specifically does this passage teach about the Holy Spirit?