1 Samuel 3:20,21 - Joseph Benson’s Commentary on the Old and New Testaments

All Israel, from Dan, &c. That is, through the whole land, from the northern bound, Dan, to the southern, Beer-sheba: which was the whole length of the land. That Samuel was established, &c. That is, settled to be a constant prophet. The Lord appeared again, &c. Having begun to appear to him in Shiloh, he continued this great favour, and revealed himself, not by dreams and visions, but by speaking to him with an audible voice, as he had done at first. And indeed he seems to have been the first eminent prophet that was raised up, after Moses, to be a public instructer and governor of God's people. Others there had been before him; but not with so high an authority and public approbation. And therefore St. Peter says, Acts 3:24, All the prophets from Samuel spake of these days; intimating, that he was the first eminent prophet whom the Lord raised up after Moses.