John Gill Commentary Luke 8:29

"For he was commanding the unclean spirit to come out from the man. For oftentimes it had seized him: and he was kept under guard, and bound with chains and fetters; and breaking the bands asunder, he was driven of the demon into the deserts." — Luke 8:29 (ASV)

For he had commanded the unclean spirit .
&c.] That had the rest of the devils under his authority, and power,

to come out of the man ;
this he had done, either before, or just as he came up to him; (See Gill on Mark 5:8).

For oftentimes it had caught him ;
possessed him, and wrought so strongly in him, and with so much fury, that there was no governing him:

and he was kept bound with chains and fetters ;
attempts were made to bind him, and keep him bound, but in vain: and he brake the bands; (See Gill on Mark 5:4).

And was driven of the devil into the wilderness :
into some desert and desolate place, where were the tombs and sepulchres of the dead; this was done by the prince of the legion.