The Lord called Samuel— The voice came, most probably, out of the most holy place. So the Chaldee renders it; a voice was heard out of the tabernacle of the Lord. Here am I, was a form of speech implying attention to what was said, and readiness to execute what was commanded.
Related Commentaries of 1 Samuel 3:4
1 Samuel 3:4
4 That the LORD called Samuel: and he answered, Here am I.