Gesenius' Hebrew Grammar/36. The Relative Pronoun
The relative pronoun (cf. § 138) is usually the indeclinable אֲשֶׁר (who, which, &c.), originally a demonstrative pronoun; see further §138 and §155. In the later books, especially Eccles. and the late Psalms, also Lam. (4 times), Jon. (Jon 17), Chron. (twice), Ezra (once),—and always in the Canticle (cf. also Ju 712, 826, 2 K 611), שֶּׁ is used instead; more rarely שַּׁ Ju 57, Ct 17 (Jb 1929?); once שָׁ before א Ju 617 (elsewhere שֶׁ before a guttural), before ה even שְׁ Ec 318, and according to some (e.g. Qimḥi) also in Ec 222. [See Lexicon, s. v.]
- The full form אשר does not occur in Phoenician, but only אש (=אֲשֶּׁ?), pronounced asse, esse (also as, es, is, ys, us), or—especially in the later Punic and in the Poenulus of Plautus—ש (sa, si, sy, su). Also in New Hebrew שֶּׁ has become the common form. Cf. Schröder, Phön. Sprache, p. 162 ff. and below, § 155; also Bergsträsser, ‘Das hebr. Präfix ש,’ in ZAW. 1909, p. 40 ff.