Albert Barnes Commentary 1 Samuel 3:1

"And the child Samuel ministered unto Jehovah before Eli. And the word of Jehovah was precious in those days; there was no frequent vision." — 1 Samuel 3:1 (ASV)

Josephus says that Samuel’s call to the prophetic office happened when he had just completed his twelfth year .

The phrase was precious means it was rare. The song of Hannah and the prophecy of the “man of God” (1 Samuel 2:27) are the only instances of prophecy since the time of Deborah. Samuel is mentioned as the first in this series of prophets (Acts 3:24).

The phrase no open vision is better translated as, “There was no vision widely proclaimed or published” (compare 2 Chronicles 31:5).