mercy. pity.
he is lunatick. moonstruck: i.e. epileptic, because epilepsy was supposed to be caused by the moon. Greek. seleniazomai. Occurs only in Matthew, here, and Matthew 4:24.
sore vexed. suffers miserably.
Related Commentaries of Matthew 17:15
Matthew 17:15
15 Lord, have mercy on my son: for he is lunatick, and sore vexed: for ofttimes he falleth into the fire, and oft into the water.