ὀμνύω
(so Hdt. and some Att.. writers) and ὄμνυμι (so generally in Att.. prose and always in Trag.; Mrk.14:71, -ύναι), [in LXX chiefly for שָׁבַע ni. ;]
to swear, affirm by oath: Mat.26:74, Mrk.14:71, Heb.7:21; before εἰ (q.v), Heb.3:11 4:3; with dative of person(s), Mrk.6:23; id. with inf., Heb.3:18; before ὅρκῳ, Act.2:30; ὀ. ὅρκον, πρός, with accusative of person(s) (cl.), Luk.1:73; with accusative (of that by which one swears; cl., see MM, xviii), Jas.5:12; before κατά, with genitive (LXX; Bl., § 34, 1), Heb.6:13, 16; before ἐν (εἰς), as in Heb. (El., § 39, 4), Mat.5:34, 36 23:16, 18 23:20-22 Rev.10:6 (Bl., § 70, 3).†
(AS)