the LORD of Hosts: God has an infinite number of angelic troops ready to do his will (see 2 Kings 6:17; Matthew 26:53). The phrase was probably meant to be an encouragement to the Judeans.
Return to me: Repentance means a complete change. It is a move away from sin and self towards loyalty to God and his covenant (see Isaiah 44:22; Malachi 3:7; see also Psalms 80:3–14; 85:4–8).