46 The Hiphil form מֵפֵר (mefer) is the participle from פָּרַר (parar, “to annul; to frustrate; to break”). It continues the doxological descriptions of God; but because of the numerous verses in this section, it may be clearer to start a new sentence with this form (rather than translating it “who …”).
47 The word is related to the verb “to think; to plan; to devise,” and so can mean “thoughts; plans; imagination.” Here it refers to the plan of the crafty that must be frustrated (see also Isa 44:25 for the contrast).
48 The word עֲרוּמִים (’arumim) means “crafty” or “shrewd.” It describes the shrewdness of some to achieve their ends (see Gen 3:1, where the serpent is more cunning than all the creatures, that is, he knows where the dangers are and will attempt to bring down the innocent). In the next verse it describes the clever plans of the wise—those who are wise in their own sight.
49 The consecutive clause showing result or purpose is simply introduced with the vav and the imperfect/jussive (see §166.a).
50 The word תּוּשִׁיָּה (tushiyyah) is a technical word from wisdom literature. It has either the idea of the faculty of foresight, or of prudence in general (see 12:6; 26:3). It can be parallel in the texts to “wisdom,” “counsel,” “help,” or “strength.” Here it refers to what has been planned ahead of time.