A.T. Robertson 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 commanded (παρηγγελλεν γαρ). Imperfect active, correct text, for he was commanding.

Often times (πολλοις χρονοις). Or "for a long time" like χρονω πολλω of verse 27 (see Robertson, Grammar, p. 537, for the plural here).

It had seized (συνηρπακε). Past perfect active of συναρπαζω, to lay hold by force. An old verb, but only in Luke in the N.T. (Luke 8:29; Acts 6:12; Acts 19:29; Acts 27:15).

Was kept under guard (εδεσμευετο). Imperfect passive of δεσμευω to put in chains, from δεσμος, bond, and that from δεω to bind. Old, but rather rare verb. Only here and Ac 22:4 in this sense. In Mt 23:4 it means to bind together. Some MSS. read δεσμεω in Lu 8:29.

Breaking the bands asunder (διαρησσων τα δεσμα). Old verb, the preposition δια (in two) intensifying the meaning of the simple verb ρησσω or ρηγνυμ, to rend.

Was driven (ηλαυνετο). Imperfect passive of ελαυνω, to drive, to row, to march (Xenophon). Only five times in the N.T. Here alone in Luke and peculiar to Luke in this incident.