God (ο θεος). This Epistle begins like Genesis and the Fourth Gospel with God, who is the Author of the old revelation in the prophets and of the new in his Son. Verses Hebrews 1:1-3 are a proemium (Delitzsch) or introduction to the whole Epistle. The periodic structure of the sentence (Hebrews 1:1-4) reminds one of Luke 1:1-4; Romans 1:1-7; 1. John 1:1-4. The sentence could have concluded with εν υιω in verse Hebrews 1:2, but by means of three relatives (ον, δι' ου, ος) the author presents the Son as "the exact counterpart of God" (Moffatt).
Of old time (παλα). "Long ago" as in Matthew 11:21.
Having spoken (λαλησας). First aorist active participle of λαλεω, originally chattering of birds, then used of the highest form of speech as here.
Unto the fathers (τοις πατρασιν). Dative case. The Old Testament worthies in general without "our" or "your" as in John 6:58; John 7:22; Romans 9:5.
In the prophets (εν τοις προφηταις). As the quickening power of their life (Westcott). So Hebrews 4:7.
By divers portions (πολυμερως). "In many portions." Adverb from late adjective πολυμερης (in papyri), both in Vettius Valens, here only in N.T., but in Wisdom 7:22 and Josephus (Ant. VIII, 3, 9). The Old Testament revelation came at different times and in various stages, a progressive revelation of God to men.
In divers manners (πολυτροπως). "In many ways." Adverb from old adjective πολυτροπος, in Philo, only here in N.T. The two adverbs together are "a sonorous hendiadys for 'variously'" (Moffatt) as Chrysostom (διαφορως). God spoke by dream, by direct voice, by signs, in different ways to different men (Abraham, Jacob, Moses, Elijah, Isaiah, etc.).