Gesenius' Hebrew Grammar/153. Restrictive and Intensive Clauses
The particles אַךְ, רַק only, serve to introduce restrictive clauses, and גַּם, אַף also, besides, even, intensive clauses. It is to be observed that the force of these particles does not necessarily affect the word which immediately follows (as is the case with אַךְ Gn 7, 34; רַק Gn 6, Am 3; even הֲרַק אַךְ hath he indeed only? Nu 12; גַּם Gn 27, Jb 7; אַף Dt 15), but very frequently extends to the whole of the following sentence. Thus with אַךְ, e.g. Nu 14, 1 K 17, Pr 17, Jb 13, 14, 16, 23; רַק Gn 20, 24, ψ 32, Pr 13; גַּם Gn 27, 32 (גַּם הִנֵּה), 44:10; 1 S 22, 28, Zc 9, Pr 17, 20; אַף Jb 14, 15.—In Mal 1 and Jb 2 גַּם is placed before two co-ordinate sentences, although, strictly speaking, it applies only to the second. Cf. the analogous examples in § 150 m.