Who were the scribes in the Old Testament?

He was one who studied the Law and meticulously copied it onto scrolls. To the end, Ezra was also a "skilled scribe" -"one who copied and studied the Law.

Ezra 7:6New King James Version (NKJV)

6 this Ezra came up from Babylon; and he was a skilled scribe in the Law of Moses, which the Lord God of Israel had given. The king granted him all his request, according to the hand of the Lord his God upon him.

As the Babylonian Exile ended, "the office of scribe came into prominence, in some ways replacing the prophet in importance, and eventually eclipsing even the role of the priest" (Nelson Study Bible, note on verse 6). Verse 11 shows Ezra's deep spiritual commitment to studying God's law, living by it and teaching it to others. He is here called "Ezra the priest, the scribe, expert in the Words of the commandments of the LORD, and of His statutes to Israel." Ezra became known in Jewish tradition "as 'the scribe's scribe' or the teacher of scribes" (note on verse 11)-considered founder of the scribal movement, which had a formative impact on the Jewish religion of Christ's day.