5:8 learned he obedience. See note on Hebrews 2:10. What He knew by omniscience, He “learned” by experience, thus “being made perfect”—not as God (for as God He was eternally perfect, by definition), but as man.

5:9 eternal salvation. There are only three adjectives used in the New Testament to describe our salvation. It is “so great salvation” (Hebrews 2:3), “eternal salvation” in this verse, and “the common salvation” (Jude 3).