And he (κα αυτος). He himself in his own person, both priest and sacrifice (Hebrews 9:14).

The propitiation (ιλασμος). Late substantive from ιλασκομα (Luke 18:13; Hebrews 2:17), in LXX, Philo, Plutarch, in N.T. only here and 1. John 4:10. Christ himself is the means of propitiation for (περ concerning) our sins. See ιλαστηριον in Romans 3:15.

For the whole world (περ ολου του κοσμου). It is possible to supply the ellipsis here of των αμαρτιων (the sins of) as we have it in Hebrews 7:27, but a simpler way is just to regard "the whole world" as a mass of sin (1. John 5:19). At any rate, the propitiation by Christ provides for salvation for all (Hebrews 2:9) if they will only be reconciled with God (2. Corinthians 5:19-21).