Albert Barnes Commentary Amos 3:13

"Hear ye, and testify against the house of Jacob, saith the Lord Jehovah, the God of hosts." — Amos 3:13 (ASV)

Hear you and testify you in—(Rather to or against) the house of Israel; first “hear” yourselves, then “testify,” that is, solemnly “protest,” in the Name of God, and “bear witness to” and “against” them, so that the solemn words may sink into them.

It is of little avail to “testify” unless we first “hear”; nor can anyone “bear witness” to what he does not know; nor will words make an “impression”—that is, leave a trace of themselves, be stamped in or on people’s souls—unless the soul that utters them has first listened to them.

Says the Lord God of hosts—“So thunders, as it were, the authority of the Holy Spirit through the mouth of the shepherd. Foretelling and protesting the destruction of the altar of Bethel, he sets his God against the god whom Israel had chosen as theirs and worshiped there, “the Lord God of hosts,” against the similitude of a calf that eateth hay (Psalms 106:20). Not I, a shepherd, but so speaks my God against your god.”