13. testify in the house, &c.—that is, against the house of Jacob. God calls on the same persons as in Am 3:9, namely, the heathen Philistines and the Egyptians to witness with their own eyes Samaria's corruptions above described, so that none may be able to deny the justice of Samaria's punishment [Maurer].
God of hosts—having all the powers of heaven and earth at His command, and therefore One calculated to strike terror into the hearts of the guilty whom He threatens.