כָּל־אִמְרַ֣ת אֱל֣וֹהַּ צְרוּפָ֑ה מָגֵ֥ן ה֝֗וּא לַֽחֹסִ֥ים בּֽוֹ׃
하나님의 말씀은 다 순전하며 하나님은 그를 의지하는 자의 방패시니라
Rashi
Every word of God is refined Heb. צרופה, refined, and He did not write anything unnecessary. [Therefore,] I should have been careful.
Ibn Ezra
Every word of God is forged — meaning, the words of the LORD are pure words, and they are the commandments forged like pure gold, and among them are wisdom of the fear of the Name, and it is not worth it to engage in anything else. Thus do not add to its words (Prov. 30:6), you, Itiel, i.e. do not add to it nor remove from it (Deut. 13:1).
Ibn Ezra
A shield — the initial mem in magen is not part of the root, as in menagen (musician), mishberei el (divine waves).