In this miracle, (Matthew 8:28-34; Mark 5:1-20; and Luke 8:26-39), Jesus Christ commands unclean spirits to come out of two men. Demons must obey Jesus even if people do not. Even so, the demons do not obey Christ's command immediately. They object, unwilling to abandon their victims. Christ could have compelled them to come out of the men immediately if He had wished, but the men may not have been able to survive the exorcism on their own strength.
In a separate incident, Mark 9:26-27 informs us, "Then the spirit [one demon] cried out, convulsed him greatly, and came out of him. And he became as one dead, so that many said, 'He is dead.' But Jesus took him by the hand and lifted him up, and he arose." Here, the exorcism had induced convulsions in the man as a single demon left him. Both exorcisms were under Christ's control; He used His great power but with wise, gentle, and cautious concern.
Jesus addresses the men as if they are possessed by a single spirit, but the demon's answer, giving his name as "Legion," shows that he led a company of demons. Mark records that the swine that the demons entered after their exorcism numbered about two thousand (Mark 5:13). If this was the number inhabiting the two men—each with its own personality, all under the power of one will, animated by one purpose and united in operation—then the plight of the two men must have been horrific in the extreme.
Martin G. Collins
The Miracles of Jesus Christ: Two Demon-Possessed Men Healed (Part Three)
It is not normal for a man to be able to break chains! Even if a man had great strength, and he pulled on the chain, he would likely do terrible damage to his wrists and ankles in breaking them off. This man was able to break chains and go on in his abnormal way, apparently without injury. While we know that Samson performed these remarkable feats of strength and endurance through the agency of God's Spirit, demons can influence human beings to do supernatural things too.
John W. Ritenbaugh
The Holy Spirit and the Trinity (Part Four)
Christ was met by the unclean men coming out of the tombs. These rock-hewn tombs were repulsive to the Jews and to dwell in them was deemed a sign of insanity. Because of the remains of the dead they contained, they were shunned by the Jews as unclean (Matthew 23:27). Under the Old Covenant, one could be physically defiled by touching a dead body. Even when a person died in a tent, the whole tent was regarded as unclean (Numbers 19:11, 14).
Unclean in Scripture means "to be defiled, polluted, unhealthy, or unfit," and refers to foods that are unfit, defilement of religious character, and moral or spiritual impurity. The word "defilement" describes a sinful and unfit condition (Isaiah 6:5). The Old Testament distinguishes between what is clean and helpful and what is unclean and unacceptable (Leviticus 10:10). The New Testament deals more with the spiritual application and lists uncleanness or moral defilement along with fornication and other sins as "works of the flesh" (Galatians 5:19-21).
In the gospels, "unclean" describes those who are possessed by demonic spirits through constant submission to evil. Uncleanness represents sin, and sin separates man from God. Because of sin, "we are all like an unclean thing" (Isaiah 64:6). Believers are not called to uncleanness but to live in holiness (I Thessalonians 4:7). We are not to yield our members to uncleanness but to righteousness and holiness (Romans 6:19).
The teaching about uncleanness springs from the concept of God's holiness (Leviticus 11:44-45). It is a miracle in itself that freedom from uncleanness and guilt is possible through God's grace. Holiness within, purity of heart, is possible through the exercise of faith in Christ's redemptive work and obedience to His truth.
Martin G. Collins
The Miracles of Jesus Christ: Two-Demon Possessed Men Healed (Part Two)
Other Forerunner Commentary entries containing Luke 8:29: