Blow ye the cornet in Gibeah, and the trumpet in Ramah: cry aloud at Bethaven, after thee, O Benjamin.
Blow ye the cornet in Gibeah. The arrival of the enemy is announced in the form of an injunction to blow an alarm.
Cornet ... trumpet - the "cornet" was made of the curved horn of animals, and was used by shepherds. The trumpet was of brass or silver, straight, and used in wars and on solemn occasions. The Hebrew is hatzotzerah, the sound imitating the trumpet note (Hosea 8:1; Numbers 10:2; Jeremiah 4:5; Joel 2:1).
Gibeah ... Ramah - both in Benjamin (Isaiah 10:29).
Cry aloud at Beth-aven - in Benjamin; not as in Hosea 4:15, Beth-el, but a town east of it, and beside Ai (Joshua 7:2). "Cry aloud" - namely to raise the alarm.
After thee, O Benjamin. The enemy is just behind thee, pursuing thee. How sad that the people of God, to whom God had promised. "I will make all thine enemies turn their backs unto thee" (Exodus 23:27), should now, on account of sin, be forced to turn their backs on their enemies! "Benjamin" is put for the whole south kingdom of Judah (cf. Hosea 5:5) being the first part of it which would meet the foe advancing from the north. "After thee, O Benjamin," implies the position of Beth-aven, behind Benjamin, at the borders of Ephraim. When the foe is at Beth-aven, he is at Benjamin's rear, close upon thee, O Benjamin (Judges 5:14).