A.T. Robertson Commentary Hebrews 5:9

"and having been made perfect, he became unto all them that obey him the author of eternal salvation;" — Hebrews 5:9 (ASV)

Having been made perfect (τελειωθεις). First aorist passive participle of τελειοω, the completion of the process of training mentioned by this same verb in 2:10 "by means of sufferings" (δια παθηματων) as stated again here in verse 8.

The author of eternal salvation (αιτιος σωτηριας αιωνιου). Common adjective from αιτια (cause), causing, often in Greek with σωτηριας (Aeschines, Philo), in N.T. only here, Luke 23:4,14,22; Acts 19:40. See same idea in Heb 2:10 (αρχηγον). See Isa 45:17.