Thomas W. Allen, E. E. Sikes, Commentary on the Homeric Hymns

[12] κοσμείσθηΝ: the dual is given in all MSS., and alteration is uncalled for. According to one tradition there were only two Horae (so on the throne of the Amyclean Apollo, Paus.iii. 18. 10, and at Athens, Paus.ix. 35. 2, although Pausanias may be mistaken in the latter case; see Robert de Gratiis Atticis, Preller-Robert i. p. 478 n. 4). For two Horae in art see Roscher Lex. i. 2723 f., 2726 f. (Rapp). Two seasons were in all probability the original number, corresponding to the old division of the year into Summer and Winter; cf. the Egyptian statues of those seasons mentioned by Herod.ii. 121.The dual may therefore keep its proper force; the following plural “ἴοιεν” is a natural irregularity. Baumeister, however, defends the dual on the ground that in late epic it was sometimes used as an equivalent of the plural verb (see on h. Apoll. 456). He thinks that the hymn-writer would follow the Hesiodean version of three Horae (Theog. 902). Although this latter supposition is uncertain, Baumeister's explanation of the dual is very probable.