Ps. 9:31 LXX

ἐν τῇ παγίδι αὐτοῦ ταπεινώσει αὐτόν, κύψει καὶ πεσεῖται ἐν τῷ αὐτὸν κατακυριεῦσαι τῶν πενήτων. -Ps. 9:31

Hello, could anyone tell me what kind of grammatical structure is ἐν τῷ αὐτὸν κατακυριεῦσαι τῶν πενήτων.

Articular infinitive

The αὐτόν is the subject of the infinitive and the genitive its object

It’s a prepositional phrase. τῷ κατακυριεῦσαι is an articular infinitive, and αυτον is the subject of the infinitive. So: “when (εν τω temporal) he (αυτον) gets dominion over the poor (κατακυριεῦσαι τῶν πενήτων).” All clear now?

Yes, thank you sirs.