What does Mark 14:17 mean?

Jesus and the twelve disciples are celebrating Passover together. As Galileans, they are accustomed to following the Mosaic law which says to sacrifice and roast the lamb at twilight on 14 Nisan (Numbers 9:5). The people from Judea follow the modified law established by Kings Hezekiah and Josiah (2 Chronicles 30:1; 35:1) and celebrate the next afternoon at the temple; since the Jewish day goes from evening to evening, it's still 14 Nisan.

John records a great deal more about this evening than the other gospels. In fact, five of John's twenty-one chapters are devoted to details of just this evening. During dinner, Jesus washes the disciples' feet (John 13:1–20), gives them a new commandment to love one another (John 13:31–35), explains that He is the way, the truth, and the life (John 14:1–14), and promises the Holy Spirit (John 14:15–31; 16:1–15). He tells the parable of the true vine and the branches (John 15:1–17), promises that the disciples will be persecuted (John 15:18–27), and goes into the implications of the resurrection (John 16:16–33). Finally, He prays for them that God will spiritually protect and equip them (John 17).

Amidst all the vital theology Jesus gives the disciples, there is an emotional undercurrent the Twelve don't quite understand. Jesus says, "I have earnestly desired to eat this Passover with you before I suffer. For I tell you I will not eat it until it is fulfilled in the kingdom of God" (Luke 22:15–16). Even with all their faults, as they bicker about who is greatest (Luke 22:24) and abandon Him (Mark 14:50), Jesus is still grateful for this last evening with His friends before He faces torture and death by crucifixion.

Now, however, it is time to release Judas so he can betray Jesus to the authorities (John 13:26–27).