A.T. Robertson Commentary Romans 16:26

"but now is manifested, and by the scriptures of the prophets, according to the commandment of the eternal God, is made known unto all the nations unto obedience of faith:" — Romans 16:26 (ASV)

But now is manifested (φανερωθεντος δε νυν). First aorist passive participle of φανεροω, to make plain, genitive case in agreement with μυστηριου.

By the scriptures of the prophets (δια γραφων προφητικων). "By prophetic scriptures." Witnessed by the law and the prophets (3:21). This thread runs all through Romans.

According to the command of the eternal God (κατ' επιταγην του αιωνιου θεου). Paul conceives that God is in charge of the redemptive work and gives his orders (1:1-5; 10:15f.). The same adjective αιωνιος is here applied to God that is used of eternal life and eternal punishment in Mt 25:46.

Unto obedience of faith (εις υπακοην της πιστεως). See 1:5.Made known unto all the nations (εις παντα τα εθνη γνωρισθεντος). First aorist passive participle of γνωριζω, still the genitive case agreeing with μυστηριου in verse 25.