Praying for the dead

The Bible tells us that after death everyone will exist for eternity in one of two places, Heaven or Hell.  Some believe that those destined for Heaven will first spend time in a place called Purgatory.  Here is the Catholic Dictionary’s definition of Purgatory:  “a place or condition of temporal punishment for those who, departing this life in God’s grace, are, not entirely free from venial faults, or have not fully paid the satisfaction due to their transgressions.”  Those who believe in purgatory also believe that the living can help those in purgatory by praying for them.

Not a hair of your head will perish

Jesus told his disciples that a time was coming when they would be persecuted for their faithfulness to him: Luke 21:12-19.  He made this promise, “Not a hair of your head will perish.”

This is a wonderful promise but it seems to contradict what Jesus said immediately before.

You will be delivered up even by parents and brothers and relatives and friends, and some of you they will put to death. You will be hated by all for my name’s sake. But not a hair of your head will perish.
Luke 21:16-18

Jesus told the disciples many of them would be put to death and immediately after promised that they would suffer no harm.  How can these two statements be reconciled?