Gesenius' Hebrew Grammar/149. Sentences which express an Oath or Asseveration
149a The particle אִם, in the sense of certainly not, and אִם־לֹא (rarely כִּי Gn 2216) in the sense of certainly, are used to introduce promises or threats confirmed by an oath (especially after such formulae as חַי־יְהֹוָה, חֵֽי־נַפְשְׁךָ, חַי אָ֫נִי, בִּי נִשְׁבַּ֫עְתִּי, &c., as well as after imprecations, see below), and also simple asseverations, e.g. 1 S 230, 2 S 2020, Jb 275 after חָלִ֫ילָה לִי far be it from me, but mostly without any introductory formula.
149b Rem. No certain explanation of these particles has yet been given. According to the usual view, phrases expressing an oath depend on the suppression of an imprecation upon oneself, e.g. the Lord do so unto me, if I do it equivalent to I certainly will not do it; then naturally אִם־לֹא properly if I do it not equivalent to I certainly will do it. It is indeed difficult to understand such self-imprecations, put into the mouth of God, as in Dt 134 f., Is 1424, 2214, Jer 226, Ez 36, 356, ψ 9511. Possibly, however, the consciousness of the real meaning of the formula was lost at an early period, and אִם־לֹא simply came to express verily, אִם verily not.—In 1 S 2522, where, instead of a self-imprecation, a curse is pronounced upon others, read לְדָוִד with the Lxx for לְאֹֽיְבֵי דָוִד.
149c (a) The particles אִם and אִם־לֹא used after the utterance of an oath and after formulae of swearing, e.g. 2 S 1111 (see note on a) חַי־יְהֹוָה וְחֵי נַפְשֶׁ֫ךָ אִם־אִֽעֱשֶׂה אֶת־הַדָּבָר הַזֶּה as the Lord liveth, and as ray soul liveth, I will not do this thing; 1 S 1445, 2 K 516 (after חַי יְהֹוָה; in 1 S 1439 and 29:6 חַי־י׳ is followed by a simple כִּי); Ct 27, 35 (after הִשְׁבַּ֫עְתִּי I adjure you); cf. also Gn 1423, 2123, 2629; spoken by God, Dt 134 f., 1 S 314, ψ 9511; similarly אִם־לֹא Gn 2437 f.; spoken by God, Is 1424, where אִם־לֹא occurs first with the perfect in the sense of a prophetic perfect, §106n, but in the parallel clause with the imperfect; Jer 226; in Gn 3152 the negative oath introduced by אִם־אָ֫נִי, אִם־אַתָּה is immediately afterwards continued by לֹא with the imperfect.—In Ez 3410 the threat introduced in verse 8 by אִם־לֹא is, after a long parenthesis, resumed with הִנְנִי.
149d (b) אִם and אִם־לֹא after formulae of cursing, e.g. 1 S 317 כֹּה יַֽעֲשֶׂה־לְּךָ אֱלֹהִים וְכֹה יוֹסִיף אִם־תְּכַחֵד מִמֶּ֫נִּי דָבָר וג׳ God do so to thee, and more also! thou shalt not hide anything from me, &c.; cf. 1 S 2522. On the other hand, כִּי follows the curse, in 1 S 1444, 1 K 223 (here with a perfect), and in 2 S 335 כִּי אִם; in 1 S 2534 the preceding כִּי is repeated before אִם; in 1 S 2013 the purport of the asseveration is repeated (after the insertion of a conditional sentence) in the perfect consecutive.
149e (c) אִם and אִם־לֹא as simple particles of asseveration, e.g. Ju 58 מָגֵן אִם־ֵי֥רָאֶה וָרֹמַח וג׳ truly, there was not a shield and spear seen, &c., Is 2214, Jb 628 (in the middle of the sentence); after חָלִ֫ילָה חָלִ֫ילָה absit, 2 S 2020; אִם־לֹא with the imperf. Is 59, with the perfect, Jb 2220.