A.T. Robertson Commentary Acts 8:28

"and he was returning and sitting in his chariot, and was reading the prophet Isaiah." — Acts 8:28 (ASV)

Was reading (ανεγινωσκεν). Imperfect active descriptive, not periphrastic like the two preceding verbs (was returning and sitting). He was reading aloud as Philip "heard him reading" (ηκουσεν αυτον αναγινωσκοντος), a common practice among orientals. He had probably purchased this roll of Isaiah in Jerusalem and was reading the LXX Greek text. See imperfect again in verse 32.