A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
jer 47:1PROPHECY AGAINST THE PHILISTINES. (Jer 47:1-7)
Pharaoh-necho probably smote Gaza on his return after defeating Josiah at Megiddo (Ch2 35:20) [GROTIUS]. Or, Pharaoh-hophra (Jer 37:5, Jer 37:7) is intended: probably on his return from his fruitless attempt to save Jerusalem from the Chaldeans, he smote Gaza in order that his expedition might not be thought altogether in vain [CALVIN] (Amo 1:6-7).
jer 47:2waters-- (Isa 8:7). The Chaldeans from the north are compared to the overwhelming waters of their own Euphrates. The smiting of Gaza was to be only the prelude of a greater disaster to the Philistines. Nebuzara-dan was left by Nebuchadnezzar, after he had taken Jerusalem, to subdue the rest of the adjoining cities and country.
jer 47:3(Compare Jer 4:29).
fathers . . . not look back to . . . children--Each shall think only of his own safety, not even the fathers regarding their own children. So desperate shall be the calamity that men shall divest themselves of the natural affections.
for feebleness of hands--The hands, the principal instruments of action, shall have lost all power; their whole hope shall be in their feet.
jer 47:4every helper--The Philistines, being neighbors to the PhÅnicians of Tyre and Sidon, would naturally make common cause with them in the case of invasion. These cities would have no helper left when the Philistines should be destroyed.
Caphtor--the Caphtorim and Philistines both came from Mizraim (Gen 10:13-14). The Philistines are said to have been delivered by God from Caphtor (Amo 9:7). Perhaps before the time of Moses they dwelt near and were subjugated by the Caphtorim (Deu 2:23) and subsequently delivered. "The remnant" means here those still left after the Egyptians had attacked Gaza and Palestine; or rather, those left of the Caphtorim after the Chaldeans had attacked them previous to their attack on the Philistines. Some identify Caphtor with Cappadocia; GESENIUS, with Crete (Eze 25:16, Cherethims); KITTO, Cyprus. Between Palestine and Idumea there was a city Caparorsa; and their close connection with Palestine on the one hand, and Egypt (Mizraim, Gen 10:13-14) on the other hand, makes this locality the most likely.
jer 47:5Baldness . . . cut thyself--Palestine is represented as a female who has torn off her hair and cut her flesh, the heathenish (Lev 19:28) token of mourning (Jer 48:37).
their valley--the long strip of low plain occupied by the Philistines along the Mediterranean, west of the mountains of Judea. The Septuagint reads Anakim, the remains of whom were settled in those regions (Num 13:28). Joshua dislodged them so that none were left but in Gaza, Gath, and Ashdod (Jos 11:21-22). But the parallel (Jer 47:7), "Ashkelon . . . the sea-shore," established English Version here, "Ashkelon . . . their valley."
jer 47:6Jeremiah, in the person of the Philistines afflicting themselves (Jer 47:5), apostrophizes the "sword of the Lord," entreating mercy (compare Deu 32:41; Eze 21:3-5, Eze 21:9-10).
up thyself--Hebrew, "Gather thyself," that is, retire or return.
jer 47:7Jeremiah, from addressing the sword in the second person, turns to his hearers and speaks of it in the third person.
Lord . . . given it a charge-- (Eze 14:17).
the sea-shore--the strip of land between the mountains and Mediterranean, held by the Philistines: "their valley" (see on Jer 47:5).
there hath he appointed it-- (Mic 6:9). There hath He ordered it to rage.
It had taken part with the Chaldeans against Judea (Kg2 24:2). Fulfilled by Nebuchadnezzar five years after the destruction of Jerusalem, when also he attacked Egypt (Jer 43:8-13) and Ammon (Jer 49:1-6). [JOSEPHUS, Antiquities, 10:9,7]. Jeremiah in this prophecy uses that of Isa. 15:1-16:14, amplifying and adapting it to his purpose under inspiration, at the same time confirming its divine authority. Isaiah, however, in his prophecy refers to the devastation of Moab by the Assyrian king, Shalmaneser; Jeremiah refers to that by Nebuchadnezzar.