According to Luke 8:31, the demons "begged Him that He would not command them to go out into the abyss." The abyss is mentioned in Romans 10:7 and several times in the book of Revelation. It appears to be a reference to Hades (i.e., the realm of departed spirits) and is distinguished from the eternal punishment of hell.
"A large herd of swine was feeding there near the mountains" (Mark 5:11). There were about 2000 of them (cf. 5:13). It was unlawful for a Hebrew to eat the flesh or touch the carcass of a pig because the animal was deemed unclean by God (cf. Lev. 11:7,8). Thus, any Jew who owned such a herd was certainly in violation of the Mosaic law. The text, however, does not state who owned the swine.
The demons begged Jesus' permission to enter the swine (Mark 5:12). They knew Jesus wouldn't give them permission to enter another human, so they asked for what they thought was the next best thing. It appears that spirits of this sort needed to possess a physical body in order to have any degree of comfort (cf. Matt. 12:43). Perhaps they assumed that the bodies of the pigs would be sufficient.
Jesus granted the request, but the result was likely not what the demons had hoped for. The swine were not created to house a spirit of any kind (whether good or evil), and the demons were not able to control them (as they would a man) once inside. The presence of the demons in their bodies made the pigs crazy and they "ran violently down the steep place into the sea, and drowned" (Mark 5:13). It is unknown exactly what became of the demons at that time.
Skeptics have often criticized Jesus for permitting this loss of property. However, there is no case against Jesus here: (1) the demons acted of their own free will and Jesus is not to be blamed (likewise, God permits men to commit evil today, but that doesn't mean He is to be blamed for it), (2) the world and everything in it belongs to God and is His to do with as He pleases (cf. Psa. 24:1), and (3) raising hogs was an unlawful Jewish business and therefore worthy of destruction (if we assume, of course, that they were owned by Jews).
Those who fed the swine quickly went and reported what had happened. Others come to the scene to investigate. They found the man who was formerly possessed by the unclean spirits "sitting and clothed and in his right mind" (Mark 5:15). The man had undergone such an amazing transformation that those who saw him were afraid. Certainly they were no longer afraid of him, but they were afraid of the One who had the power to bring about this drastic change--Jesus!
From a human perspective, this demoniac was untamable, but not for Jesus. The great tempest was no match for His power and neither was Legion.
We will conclude studying this context in our next lesson.