Concise Bible Dictionary:
God so ordained it that by the rise of the Greek empire this language was spread over Asia Minor, Syria, Egypt, and countries adjacent, and it is a language still understood by the learned of all nations. It is acknowledged to be a remarkably flexible language, capable of forming new theological terms with delicate shades of meaning, and of expressing ideas with precision. It was therefore, on all accounts, the most suitable language in which to make known the gospel of God, and the truths needed for the building up of the saints. Not only was the New Testament written in Greek, but the Old Testament was also translated into the same language, and that version was quoted by both the Lord and His apostles. The chief captain at Jerusalem, though a Roman, asked Paul if he could speak Greek, supposing him to be an Egyptian (Acts 21:37). The inscription placed over the Lord at His crucifixion was written in Greek as well as in Hebrew and Latin: all the world must be informed who it was that hung upon that cross (Luke 23:38; John 19:20). The name and character of the angel of the bottomless pit was also proclaimed in Hebrew and Greek (Rev. 9:11).