Clement of Alexandria on who wrote Hebrews (via Eusebius):

He [Clement] says that the Epistle to the Hebrews is the work of Paul, and that it was written to the Hebrews in the Hebrew language. Luke however, translated it carefully to make it available for the Greeks and for this reason the same style of expression is found in this epistle and in the Acts. (Eusebius, Historia Ecclesiastica 6.14.2)

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