Thus saith the LORD; For three transgressions of Gaza, and for four, I will not turn away the punishment thereof; because they carried away captive the whole captivity, to deliver them up to Edom:
For three transgressions of Gaza - the southernmost of the five capitals of the five divisions of Philistia, and the key to Palestine on the south: hence, put for the whole Philistine nation. Uzziah commenced the fulfillment of this prophecy (see 2 Chronicles 26:6).
Because they carried away captive the whole captivity - i:e., they left none. Compare with the phrase here Jeremiah 13:19, "Judah shall be carried away captive all of it, it shall be wholly carried away." Under Jehoram already the Philistines had carried away all the substance of the King of Judah, and his wives and his sons, "so that there was never a son left to him, except Jehoahaz;" and after Amos' time (if the reference include the future, which to the prophet's eye is as if already done), under Ahaz, they seized on all the cities and villages of the low country and south of Judah (2 Chronicles 28:18).
To deliver them up to Edom - Judah's bitterest foe; as slaves (Amos 1:9; cf. Joel 3:1; Joel 3:3; Joel 3:6). Grotius refers it to the fact that, on Sennacherib's invasion of Judah, many fled for refuge to neighbouring countries; the Philistines, instead of hospitably sheltering the refugees, sold them, as if captives in war, to their enemies, the Idumeans. Compare Isaiah 16:4. "Let mine outcasts dwell with thee, Moab: be thou a covert to them from the face of the spoiler."