Verse 21: Then the children of Reuben and the children of Gad and the half tribe of Manasseh answered, and said unto the heads of the thousands of Israel…
[To the prince of the legation of Israel] Hebrew: unto the heads of the thousands, that is, of the Israelite people, which was exceedingly great in number (Vatablus).
The heads of the thousands of Israel: Either, first, properly, each was a governor of a thousand; for there were among them divers rulers, some of tens, some of hundreds, and some of thousands; or rather, secondly, improperly, and indefinitely, that is, of the people of Israel, which consist of so many thousands more than you, whose authority therefore you owe a reverence to. For by comparing verse 14, these seem to be greater persons than those that were rulers of thousands.
Verse 22: The LORD (Deut. 10:17) God of gods, the LORD God of gods, he (1 Kings 8:39; Job 10:7; 23:10; Ps. 44:21; 139:1, 2; Jer. 12:3; 2 Cor. 11:11, 31) knoweth, and Israel he shall know; if it be in rebellion, or if in transgression against the LORD, (save us not this day)…
[God most mighty, etc., אֵל֩׀ אֱלֹהִ֙ים׀ יְהוָ֜ה] God of gods, the Lord (Jonathan, Munster, Pagnine, Montanus, Tigurinus), that is, who alone ought to be called God (Vatablus). Now, He is called the God of gods, that is, of Angels or Princes (Hebrews in Masius). There is πάθος/pathos in that Epizeuxis, and in the name God of gods; that is to say, that highest and true God (Piscator). It is repeated for the greater confirmation (Vatablus). A collection of the three principal names of God, especially repeated, carries the greatest weight: as if by no speech are they sufficiently able to bring in God as a present witness of their intention, although they have an exceedingly great desire to do so (Masius). Now, these three names are suitable for this place, by which the three principal attributes of God are attested: 1. power; אֵל/El, that is, the powerful: 2. righteousness; אֶלוֹהִים/Elohim, that is, God the governor, judge, and defender of all: 3. majesty; יְהוָה/Jehovah, that is, being itself (or, the fount of being [Bonfrerius]). אֵל/El indicates that the power to punish their sins is not wanting to God: By the name אֶלוֹהִים/Elohim they acknowledge that they are in the eyes of God, and that they are not able to evade punishment before the most righteous Judge: By the third term they show that with respect to all their being they depend upon God, and that hence, if they swear falsely, they for good reason fear that He is going to take away their life and being (Bonfrerius). Therefore, they that address God with those names, and who then say, He knows, let Him avenge, think very highly of God. Undoubtedly he that professes these things briefly comprehends the sum of all Theology (Masius). The modesty of those that without any abuse calmly refute that most terrible charge is here to be admired. Would that Christians might imitate this moderation; and that they might not take pleasure in cutting their adversaries with impious curses, but rather in modestly teaching, or certainly confuting, them with strong arguments. Moreover, an oath (which they employ here) is then lawful to employ, since the fact is otherwise uncertain, and lies shut up in the souls of men, Exodus 22:11, especially if the matter treated be great. For to appeal continually to God in the most trifling causes appears to be contrary to the majesty of God, and is not without danger of perjury (Masius).
The Lord God of gods; that Jehovah whom we, no less than you, acknowledge and adore as the God of gods, infinitely superior to all that are called gods. The multiplying of his titles, and the repetition of these words, show their zeal and earnestness in this matter, and their abhorrency of the very thoughts of it. He knoweth; to him we appeal who knoweth all things, and the truth of what we are now saying.
[And Israel shall also know] Namely, when they shall observe that they uphold the Religion of their ancestors with great constancy (Masius). This addition is not superfluous, since a great many, so that they evade the prompt judgment of other men concerning themselves, and avoid punishment, do not fear to appeal to God as witness, whose slowness in vengeance they despise (Masius).
Israel he shall know; not only our present words, but our future and constant course shall satisfy all Israel of our perseverance in the true religion.
[If with an intention of transgression, etc.,אִם־בְּמֶ֤רֶד וְאִם־בְּמַ֙עַל֙ בַּֽיהוָ֔ה אַל־תּוֹשִׁיעֵ֖נוּ] If in rebellion, or in transgression (supply, either, this was done [Tigurinus], or, we acted sinfully [Munster]) thou (supply, O Lord [Munster, Vatablus]) will not keep, or, keep not, us (Munster, similarly Masius, Vatablus, Junius and Tremellius, Jonathan, Syriac). That is to say, let God destroy us, if with this intention we have done this, etc. (Vatablus). They address God in the second person, as present (Masius). It is an emotional speech, and so it consists of clipped members (Junius). Others: let Him not save us today (Syriac, Arabic). It could indeed appear that that, save thou us not today, has been spoken to Phineas, as the leader of the legation, in this sense, We do entreat that even today thou wouldst not assail us with battle, if we have committed such an outrage. But the other opinion better agrees with the great emotions that they display in the entire speech, and is also proven from the Hebrew words (Masius).
If it be; if this have been done by us with such design, or in such a manner. Save us not this day; thou, O Lord, to whom we have appealed, and without whom we cannot be saved or preserved, save us not from any of our enemies, nor from the sword of our brethren. It is a sudden apostrophe to God, usual in such vehement speeches.
 Hebrew: וַֽיַּעֲנוּ֙ בְּנֵי־רְאוּבֵ֣ן וּבְנֵי־גָ֔ד וַחֲצִ֖י שֵׁ֣בֶט הַֽמְנַשֶּׁ֑ה וַֽיְדַבְּר֔וּ אֶת־רָאשֵׁ֖י אַלְפֵ֥י יִשְׂרָאֵֽל׃
 Hebrew: אֶת־רָאשֵׁ֖י אַלְפֵ֥י.
 Hebrew: אֵל֩׀ אֱלֹהִ֙ים׀ יְהוָ֜ה אֵ֣ל׀ אֱלֹהִ֤ים׀ יְהוָה֙ ה֣וּא יֹדֵ֔עַ וְיִשְׂרָאֵ֖ל ה֣וּא יֵדָ֑ע אִם־בְּמֶ֤רֶד וְאִם־בְּמַ֙עַל֙ בַּֽיהוָ֔ה אַל־תּוֹשִׁיעֵ֖נוּ הַיּ֥וֹם הַזֶּֽה׃
 That is, the repetition of words or phrases for emphasis.
 See Philippians 4:5.