Commentaries:
Robertson's Word Pictures (NT)
A minister of the circumcision (diakonon peritomhv). Objective genitive, "a minister to the circumcision." Diakonon is predicate accusative with gegenhsqai (perfect passive infinitive of ginomai in indirect assertion after legw, I say) and in apposition with Xriston, accusative of general reference with the infinitive. See Galatians 4:4 f.
That he might confirm (eiv to bebaiwsai). Purpose clause with eiv to and the infinitive bebaiwsai (first aorist active of bebaiow, to make stand).
The promises given unto the fathers (tav epaggeliav twn paterwn). No "given" in the Greek, just the objective genitive, "the promises to the fathers." See Romans 9:4-5.
Other Robertson's Word Pictures (NT) entries containing Romans 15:8:
Romans 15:13
Romans 15:16
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