Q. In the story where Jesus drives demons out a possessed man and into a herd of pigs, the demons implore him not to send them to the abyss. Why did Jesus have mercy on the demons? Does he feel compassion even towards those who are with the devil?
Also, though Jesus never sinned, why was it not wrong for Jesus to send the demons into the herd of pigs, thus driving the herd off a cliff, if he knew that it would cost the owner of the swine greatly to lose his whole herd? Jesus could have just ordered the demons to the abyss, and that would not have cost the swineherd so much. Who knows, it might have ruined the swineherd’s livelihood and put him in great debt. Why didn’t Jesus save the swineherd from losing all of his pigs, and keep the pigs from dying if he had the option to?
I personally don’t think that in this episode Jesus was showing mercy to the demons or having compassion on them. The gospel writers typically tell us explicitly when Jesus is acting out of compassion (for example, “When Jesus landed and saw a large crowd, he had compassion on them and healed their sick”). But there is no reference to this in any of the three parallel accounts of this episode, in Matthew, Mark, or Luke. Rather, Mark and Luke say that Jesus “gave them permission” to enter the pigs, and Matthew says that he commanded the demons, “Go!”
So if Jesus was not motivated by mercy or compassion, what might have been his motive in agreeing to the demons’ request to enter the pigs? I believe he did this not because the demons asked, but because when they asked, he recognized that it would be strategic for the proclamation of the kingdom of God if he agreed.
The fact that the entire large herd of pigs—two thousand, according to Mark—rushed down the bank and drowned in the lake shows that Jesus indeed cast a huge host of demons out of the afflicted man. (They called themselves “Legion, for we are many”; a Roman legion had several thousand soldiers.) Presumably if there had only been one demon, or just a few, only that many pigs would have rushed away. But when thousands of pigs were affected, this was evidence of a very powerful exorcism, showing that the kingdom of God had indeed come with great power in the person and ministry of Jesus.
To answer the second part of your question, it may be that Jesus realized that such a demonstration would be worth making to everyone in the area, including the swineherd, even if it cost the swineherd his entire livelihood. Jesus told the parables of the hidden treasure and the pearl of great value to illustrate how finding the kingdom of God is worth giving up “everything we have.” It’s a bit like when Jesus told his first disciples to “follow me” and they left behind their fishing boats and nets. The one difference is that the disciples got to choose ahead of time to leave everything behind and follow Jesus, while the swineherd would have had to realize after the fact that losing everything was worth finding out about Jesus’ great power and love and choosing to follow him.
We don’t hear anything more about the swineherd in the story, but we do hear about the man who was delivered from the demons. He wanted to leave his family, friends, and home country behind and travel with Jesus and his disciples proclaiming the kingdom of God. But Jesus recognized that he would be a more strategic witness right there in his home country and so he told him, “Return home and tell how much God has done for you.” Maybe Jesus had the same thing in mind for the swineherd, if he too realized that the kingdom he had just seen come in such great power, bringing liberation, was worth everything to obtain.