78 Or “the Lord will be at your side.” Assuming that the noun כֶּסֶל (kesel) is related to the root II כָסַל (“confidence”; 492 כֶּסֶל 3), the preposition ב (bet) introduces the predicate noun כִּסְלֶךָ (kislekha, “your confidence”) and functions as a beth essentiae ( §119.i) which emphasizes the quality or nature of the noun ( 88 בְּ 7; בְּ 3): “the Lord will be your confidence.” However, if the noun is related to I כסל (“loins; side”; I כֶּסֶל 2), the preposition ב (bet) would function in a locative sense: “the Lord will be at your side.” See on the following phrase “source of your confidence.”
79 Heb “your confidence” (so , , ) or “at your side.” There is debate whether the term כֶּסֶל (kesel) is related to the root I כָסַל “loins; side” (so I כֶּסֶל 2) or II כָסַל “confidence” (so 492 כֶּסֶל 3). The relates it to I כָסַל and offers “the Lord will be at your side (latus).” Others relate it to II כָסַל “confidence” (e.g., Job 8:14; 31:24; Ps 78:7) and take it as a metonymy (= confidence) of adjunct (= object of confidence): “the Lord will be the source [or, object] of your confidence.”
80 The term רַגְלְךָ (raglekha, “your foot”) functions as a synecdoche of part (= your foot) for the whole person (= you). This synecdoche develops the extended comparison between the hunter’s snare and calamity that afflicts the wicked.
81 Heb “from capture.” The noun לָכֶד (lakhed, “capture; snare”) occurs only here in OT ( 540 ; לֶכֶד). It is figurative for the calamity of v. 25. God will protect the wise (or, righteous) from the consequences of sin (snares) that afflict the wicked.