A.T. Robertson Commentary Hebrews 1:11

"They shall perish; but thou continuest: And they all shall wax old as doth a garment;" — Hebrews 1:11 (ASV)

They (αυτο). The heavens (ουρανο).

Shall perish (απολουντα). Future middle of απολλυμ. Modern scientists no longer postulate the eternal existence of the heavenly bodies.

But thou continuest (συ δε διαμενεις). This is what matters most, the eternal existence of God's Son as Creator and Preserver of the universe (John 1:1–3; Colossians 1:14ff.).

Shall wax old (παλαιωθησοντα). First future passive indicative of παλαιοω, from παλαιος, for which see Lu 12:33; Hebrews 8:13.