Who had his dwelling among the tombs; and no man could bind him, no, not with chains:

People's New Testament

5:3 Dwelling among the tombs. The tombs of that age were either natural or artificial caves in a rocky hillside, and hence would afford shelter. They are now sometimes the homes of the poorer classes.

No man could bind him. Modern lunatics in their frenzy often exhibit almost superhuman strength.

Jamieson-Fausset-Brown Bible Commentary

3. Who had his dwelling among the tombs-Luke (Lu 8:27) says, "He ware no clothes, neither abode in any house." These tombs were hewn out of the rocky caves of the locality, and served for shelters and lurking places (Lu 8:26).

Matthew Henry's Concise Commentary

5:1-20 Some openly wilful sinners are like this madman. The commands of the law are as chains and fetters, to restrain sinners from their wicked courses; but they break those bands in sunder; and it is an evidence of the power of the devil in them. A legion of soldiers consisted of six thousand men, or more. What multitudes of fallen spirits there must be, and all enemies to God and man, when here was a legion in one poor wretched creature! Many there are that rise up against us. We are not a match for our spiritual enemies, in our own strength; but in the Lord, and in the power of his might, we shall be able to stand against them, though there are legions of them. When the vilest transgressor is delivered by the power of Jesus from the bondage of Satan, he will gladly sit at the feet of his Deliverer, and hear his word, who delivers the wretched slaves of Satan, and numbers them among his saints and servants. When the people found that their swine were lost, they had a dislike to Christ. Long-suffering and mercy may be seen, even in the corrections by which men lose their property while their lives are saved, and warning given them to seek the salvation of their souls. The man joyfully proclaimed what great things Jesus had done for him. All men marvelled, but few followed him. Many who cannot but wonder at the works of Christ, yet do not, as they ought, wonder after him.