Charles Ellicott Commentary Amos 6:13

"ye that rejoice in a thing of nought, that say, Have we not taken to us horns by our own strength?" — Amos 6:13 (ASV)

A thing of nothing refers to the calf-worship, the idol that Israel is glorying and trusting in, the idolatrous travesty of the Eternal that they call “the excellency of Jacob” (Compare to Amos 6:8 and Amos 8:7).

Taken to us horns — that is, instruments of resistance and aggression, the horn being symbolic of strength (Jeremiah 48:25; Psalms 75:10; Psalms 89:17; Psalms 92:10; 1 Samuel 2:10). The sacred historian takes quite a different view of the success of Jeroboam II (2 Kings 14:26–27). These boasters reckoned the success of arms as due to their own ingenuity or “power” (Compare to the language put into the mouth of Pharaoh by Ezekiel 29:3: My river is my own: I made it for myself.).