What does Mark 14:25 mean?

The "fruit of the vine" is wine. Jesus acknowledged to the Pharisees and scribes that He drank wine (Luke 7:28–35), and He made wine for a wedding (John 2:6–11). This does not mean that Christians must drink alcohol or even that they should drink alcohol, just that we may. We may not get drunk, use it to escape the worries of life, or drink if it leads us to ungodly behavior (Proverbs 20:1; Ephesians 5:18). We should not drink if we think we're prone to addiction (1 Corinthians 6:12; 2 Peter 2:19) or if it would tempt someone around us to act against their conscience (1 Corinthians 8:9–13). But if no biblical restrictions are being broken, it is not for another believer to condemn someone who chooses to drink (Romans 14:1–4).

And, yet, that's not what this verse is about. The Bible says that wine is for celebration (Psalm 104:14–15). Jesus and the disciples are celebrating the Passover which falls the day before the great feast shared on the first day of the Feast of Unleavened Bread. But, by that day, Jesus will be buried in the tomb. Even on the cross, when offered wine mixed with a mild analgesic, Jesus refuses it (Matthew 27:34).

The traditional Passover meal is a long, liturgical affair. Throughout the various statements and courses of food, four cups of wine are drunk, representing the four phases of redemption in Exodus 6:6–7: "I will bring you out…I will deliver you from slavery to them…I will redeem you…I will take you to be my people, and I will be your God." Some scholars say Jesus is making His statement of abstinence between the third and fourth cups. He is about to fulfill the first three promises on the cross, but the fourth will not be until the end times. Jesus promises to drink wine again in a time and place suitable for celebration. It may be at the marriage supper of the Lamb (Revelation 19:7–10), likely after the rapture ("…take you to be my people…"), when He will finally be "married" to the church.