A.T. Robertson Commentary Hebrews 1:6

"And when he again bringeth in the firstborn into the world he saith, And let all the angels of God worship him." — Hebrews 1:6 (ASV)

And when he again bringeth in (οταν δε παλιν εισαγαγη). Indefinite temporal clause with οταν and second aorist active subjunctive of εισαγω. If παλιν is taken with εισαγαγη, the reference is to the Second Coming as in 9:28. If παλιν merely introduces another quotation (Psalms 97:7) parallel to κα παλιν in verse 5, the reference is to the incarnation when the angels did worship the Child Jesus (Luke 2:13f.). There is no way to decide certainly about it.

The first-born (τον πρωτοτοκον). See Ps 89:28. For this compound adjective applied to Christ in relation to the universe see Col 1:15, to other men, Romans 8:29; Colossians 1:18, to the other children of Mary, Luke 2:7; here it is used absolutely.

The world (την οικουμενην). "The inhabited earth." See Ac 17:6.

Let worship (προσκυνησατωσαν). Imperative first aorist active third plural of προσκυνεω, here in the full sense of worship, not mere reverence or courtesy. This quotation is from the LXX of De 32:43, but is not in the Hebrew, though most of the LXX MSS. (except F) have υιο θεου, but the substance does occur also in Ps 97:7 with ο αγγελο αυτου.