Question: "What does it mean to grieve / quench the Holy Spirit?"
Answer: When the word “quench” is used in Scripture, it is speaking of suppressing fire. When believers put on the shield of faith, as part of their armor of God (Ephesians 6:16), they are extinguishing the power of the fiery darts from Satan. Christ described hell as a place where the fire would not be “quenched” (Mark 9:44, 46, 48). Likewise, the Holy Spirit is a fire dwelling in each believer. He wants to express Himself in our actions and attitudes. When believers do not allow the Spirit to be seen in our actions, when we do what we know is wrong, we suppress or quench the Spirit (1 Thessalonians 5:19). We do not allow the Spirit to reveal Himself the way that He wants to.
To understand what it means to grieve the Spirit, we must first understand that this indicates the Spirit possesses personality. Only a person can be grieved; therefore, the Spirit must be a divine person in order to have this emotion. Once we understand this, we can better understand how He is grieved, mainly because we too are grieved. Ephesians 4:30 tells us that we should not grieve the Spirit. We grieve the Spirit by living like the pagans (4:17-19), by lying (4:25), by being angry (4:26-27), by stealing (4:28), by cursing (4:29), by being bitter (4:31), by being unforgiving (4:32), and by being sexually immoral (5:3-5). To grieve the Spirit is to act out in a sinful manner, whether it is in thought only or in both thought and deed.
Both quenching and grieving the Spirit are similar in their effects. Both hinder a godly lifestyle. Both happen when a believer sins against God and follows his or her own worldly desires. The only correct road to follow is the road that leads the believer closer to God and purity, and farther away from the world and sin. Just as we do not like to be grieved, and just as we do not seek to quench what is good—so we should not grieve or quench the Holy Spirit by refusing to follow His leading.