Hear ye; Septuagint, ἱερεῖς ἀκούσατε, "Hear, O ye priests." The address is to the heathen, already summoned (Amos 3:9) to witness the sins of Israel, and now called to witness her punishment, In the house; better, against the house of Jacob, the tribes of Israel (Amos 3:1).
God of hosts. God of the powers of heaven and earth, and therefore able to execute his threats. Septuagint, ὁ παντοκράτωρ, "the Almighty."