Luke 12:4

“And I say to you my friends, Do not be afraid of those who kill the body, and after that have no more that they can do.”

This is the only place in the first three Gospels where Jesus calls His disciples His ‘friends', but compare also John 15:13, where we learn that those are His friends who obey His words, and that to them He reveals His secrets. This tenderness is in order to strengthen them to face the stark fact, baldly stated, that they might be martyred. But even in the face of that they should remember that once they have been killed their enemies will be powerless to do anything more. Whatever they do to their bodies it will not affect their future (there were times in the future when because of their belief in the resurrection men maltreated the bodies of Christians and sought to dispose of them in such a way that they could not rise again, but all would be to no avail). So in view of that fact they need not be afraid of them, for God will watch over them and is so concerned about them that He even knows how many hairs they have on their head. Whatever is done to their bodies He will be able to resurrect them as one whole.