What does Matthew 8:32 mean?
Jesus is casting demons out of two possessed men (Matthew 8:28–29). From Mark's and Luke's telling of this story, we know that at least one of the men is possessed by a great number of demons. The demons have recognized Jesus as the Son of God and have asked if He is there to torment them. They have begged Him to send them into a herd of pigs visible in the distance on a hillside, rather than sending them to the abyss (Matthew 8:30–31). We know from Mark that this herd consisted of about 2,000 pigs (Mark 5:13).Now Jesus agrees to their request with a one-word command: "Go." What happens next is dramatic and violent. The demons travel from the two men into the herd of pigs, causing a stampede straight down a steep hill and into the Sea of Galilee. All the pigs drown.
Despite human obsessions with angels and demons, Scripture gives few details about these beings. This verse reveals one of the few firmly known facts about demons: they can possess animals. The Bible doesn't specify whether the demons intended to drown the pigs, or if this was an unexpected result of getting what they requested from Jesus. Of course, it was no surprise to Him. It is also not known what became of the demons after the pigs drowned. Jewish tradition said demons could be killed, but the Bible teaches they are eternal beings. In that case, the demons either remained in the pigs at the bottom of the Sea of Galilee, were freed to roam, or were bound to somewhere else, after all.
We also cannot answer, biblically, why Jesus granted the request to enter pigs when He knew what would happen next. This would have incurred a great cost to their Gentile owners. That is likely part of the reason the people ask Him to leave their region in the following verses.