פירוש על שמואל א 9:17

Will rule over My people. Will restrain [=will rule], similar to 'restrained [עָצוּר] and let free.'⁹Devarim 32:36. This is the function of the ruler, to restrain the people during war, that they not scatter or spread out one from another, and¹⁰In the time of peace… to restrain each one from doing evil.¹¹The phrase may be translated as “he will restrain them [the Philistines] from [attacing] My people”.—Radak In our language, we call מַעֲצוֹרdestenir, in O.F.

He explained to him that what was meant by "he will save them from the Plishtim" is that he would inspire them to abandon their evil ways and through this he would merit to save them, and actually save them.