Hebrews 5:9

καὶ τελειωθεὶς … αἰωνίου “and having [thus] been perfected became to all who obey Him the source [originator] of eternal salvation”. τελειωθείς (v. Hebrews 2:10) having been perfectly equipped with every qualification for the priestly office by the discipline already described. Several interpreters (Theodoret, Bleek, Westcott) include in the word the exaltation of Christ, but illegitimately. The word must be interpreted by its connection with ἔμαθεν ὑπακοήν; and here it means the completion of Christ's moral discipline, which ended in His death. He thus became αἴτιος σωτηρίας αἰωνίου author, or cause of eternal salvation, in fulfilment of the call to an eternal priesthood, Hebrews 5:6 εἰς τὸν αἰῶνα and Hebrews 5:10. αἴτιος frequently used in a similar sense from Homer downwards, as in Diod. Sic., iv. 82, αἴτιος ἐγένετο τῆς σωτηρίας. Aristoph., Clouds, 85, οὗτος γὰρ ὁ θεὸς αἴτιός μοι τῶν κακῶν. Philo, De Agri., 22, πᾶσι τοῖς ὑπακούουσιναὐτῷ with a reference to τὴν ὑπακ. of Hebrews 5:8. The saved must pass through an experience similar to the Saviour's. Their salvation is in learning to obey. Thus they are harmonised to the one supreme and perfect will. This is reversely given in Hebrews 2:10.