What does Mark 14:23 mean?

We don't have many details about how the Passover was observed in Jesus' time. It was probably more involved than the simple meal of lamb, unleavened bread, and bitter herbs that God originally established (Exodus 12:8), but not as elaborate as the meal Jews celebrate now. The modern Seder didn't come into being until after AD 70. When the temple and Jerusalem were destroyed by the Romans and the Jews scattered, scribes wrote down the extra-scriptural Oral Law so it wouldn't be lost; it includes the specifics of the Seder. This is the same "law" that Jesus condemned the Pharisees for valuing over the instructions God gave them (Mark 7:1–13). That doesn't mean that the Seder is wicked or contrary to the Law, just that Jews are not required to celebrate the Passover with such pomp and circumstance.

Today, the Seder wine may be diluted or even replaced with grape juice, depending on which scholar the family follows. No matter the alcohol content, Jesus drank wine and gave wine—"the fruit of the vine" found in Mark 14:25—to the disciples to drink. He acknowledges drinking wine in Luke 7:33–35. He doesn't get drunk. He drinks in accordance with the Old Testament, in celebration (Psalm 104:14–15). This does not mean that every Christian should drink. But to declare that all Christ-followers should avoid all alcohol is akin to the same manmade rules that Jesus preached against.

The text is clear that Jesus and the disciples drink from one cup. To drink from someone's cup is to accept a deep relationship with them. When Jesus asked James and John if they would share His destiny, He said, "Are you able to drink the cup that I drink…?" (Mark 10:38). When the disciples drink the cup of wine that represents Jesus' blood, they identify with Him in a stronger way than they realize. That drink represents accepting the work of Jesus on the cross, taking it into themselves and changing their hearts. It does the same for believers when we share the Lord's Supper today.