As thy sword hath made women childless - It appears that Agag had forfeited his life by his own personal transgressions, and that his death now was the retribution of his cruelties.
And Samuel hewed Agag in pieces -
2. It is not likely he did it by his own sword, but by that of an executioner. What kings, magistrates, and generals do, in an official way, by their subjects, servants, or soldiers, they are said to do themselves; qui facit per alterum, facit per se.
Hewed in pieces - Only found in this passage. Samuel thus executed the חרם chērem 1 Samuel 15:3 which Saul had violated, and so both saved the nation from the guilt of a broken oath, and gave a final example to Saul, but apparently in vain, of uncompromising obedience to the commandments of God. There is something awful in the majesty of the prophet rising above and eclipsing that of the king (compare 1 Kings 21:20; Jeremiah 38:14 ff; Daniel 2:46; Daniel 4:27).