Hebrews 1:2 New English Translation

²in these last days he has spoken to us in a son,^[a] whom he appointed heir of all things, and through whom he created the world.^[b]

Hebrews 1:2 tn The Greek puts an emphasis on the quality of God’s final revelation. As such, it is more than an indefinite notion (“a son”) though less than a definite one (“the son”), for this final revelation is not just through any son of God, nor is the emphasis specifically on the person himself. Rather, the focus here is on the nature of the vehicle of God’s revelation: He is no mere spokesman (or prophet) for God, nor is he merely a heavenly messenger (or angel); instead, this final revelation comes through one who is intimately acquainted with the heavenly Father in a way that only a family member could be. There is, however, no exact equivalent in English (“in son” is hardly good English style).sn The phrase in a son is the fulcrum of Heb 1:1-4. It concludes the contrast of God’s old and new revelation and introduces a series of seven descriptions of the Son. These descriptions show why he is the ultimate revelation of God.
Hebrews 1:2 tn Grk “the ages.” The temporal (ages) came to be used of the spatial (what exists in those time periods). See Heb 11:3 for the same usage.

New English Translation (NET)