What does Mark 10:38 mean?
Jesus' rebuke to James and John appears surprisingly gentle. Perhaps this is because He knows they will suffer for Him and the gospel before they receive any glory.To "drink someone's cup" means to share in their fate. The tense used for the verb "drink" here may mean that Jesus is in the process of drinking, not that the "cup" is yet to come. But it also may refer to an action in the future that is so assured it can be considered already present. The Old Testament frequently uses "the cup of God's wrath" as a metaphor for His judgment for humanity's rebellion against Him (Psalm 75:8; Isaiah 51:17; Ezekiel 23:31–34). It is this "cup" that Jesus drinks when He hangs on the cross, the Father's face turned away (Mark 15:34).
The reason Jesus came is so that we will not have to drink the cup of God's wrath, and Jesus does not ask us to drink the cup of God's wrath with Him. He asks us to drink the cup of His blood, so we are covered by His sacrifice and protected from God's wrath (Mark 14:22–25), as the Israelites were during the Passover (Exodus 12).
In our churches today, we drink the cup, symbolic of that blood, at the Lord's Supper. This shows our oneness with the church and our acceptance of a joined fate, including the persecution needed to further the gospel (Colossians 1:24) and the glorious marriage of the Lamb and the church (Revelation 19:6–10). Those who reject Jesus in the tribulation will feel the full cup of God's wrath, however, as God's judgment rains down on the world (Revelation 6—18).
In Greek culture, baptism is a metaphor for being overwhelmed or immersed in something. This is similar to the modern cliché "baptized by fire" used when we mean overwhelmed by challenges from the beginning. Jesus is, in a sense, baptized or immersed in our sins and God's wrath on the cross (1 Peter 2:24; 2 Corinthians 5:21). But this meaning is not familiar to the Jews of Jesus' time although Isaiah did use it (Isaiah 30:27–28). At the time, baptism was a sign that one followed the teachings of a specific rabbi or school. In Jesus' ministry, people are baptized as a sign of their repentance from sin, and we apply this meaning, as well. After the crucifixion and resurrection, the symbolism of baptism becomes richer. Now, baptism is a metaphor for dying to sin and rising again in new life in Christ (Romans 6:3–4; Colossians 2:12).