ο relative pronoun - accusative singular neuter
hos  hos: the relatively (sometimes demonstrative) pronoun, who, which, what, that -- one, (an-, the) other, some, that, what, which, who(-m, -se), etc.
προεπηγγειλατο verb - aorist middle deponent indicative - third person singular
proepaggellomai  pro-ep-ang-ghel'-lom-ahee:  to promise of old -- promise before.
dia  dee-ah': through (in very wide applications, local, causal, or occasional)
των definite article - genitive plural masculine
ho  ho: the definite article; the (sometimes to be supplied, at others omitted, in English idiom) -- the, this, that, one, he, she, it, etc.
προφητων noun - genitive plural masculine
prophetes  prof-ay'-tace: a foreteller (prophet); by analogy, an inspired speaker; by extension, a poet -- prophet.
αυτου personal pronoun - genitive singular masculine
autos  ow-tos': the reflexive pronoun self, used of the third person , and (with the proper personal pronoun) of the other persons
en  en: in, at, (up-)on, by, etc.
γραφαις noun - dative plural feminine
graphe  graf-ay': a document, i.e. holy Writ (or its contents or a statement in it) -- scripture.
αγιαις adjective - dative plural feminine
hagios  hag'-ee-os: sacred (physically, pure, morally blameless or religious, ceremonially, consecrated) -- (most) holy (one, thing), saint.