Jesus answered them and said, “You do not know what you are asking. Are you able to drink the cup that I am going to drink, or be baptized with the baptism with which I am going to be baptized?”
Christ exposes the ignorance of their request. They were asking for places of glory, but they did not understand that to share in that glory also means the cup of suffering and the baptism of death. In Holy Scripture, the “cup” often means the portion that God gives to a person, whether of joy or of judgment, and here it means the portion of Christ’s sufferings. The “baptism” here portrays the complete immersion into suffering that the Lord is to endure. He does not drive them away, but asks whether they are ready truly to bear the path at whose end is glory.