Numbers 21:34

The Lord said unto Moses, Fear him not--a necessary encouragement, for Og's gigantic stature (Deu 3:11) was calculated to inspire terror. He and all his were put to the sword.

Next: Numbers Chapter 22

Jamieson, Fausset & Brown — Commentary Critical and Explanatory on the Whole Bible (1871) — public domain (CC PDM 1.0). Text via the HelloAO Bible API.

34. Edrei] the modern Edre‘ât or Der‘ât, appears to have been the second royal city of Bashan; cf. Deu_1:4, Jos_12:4; Jos_13:12. It lay on the southern border of Bashan (Deu_3:1; Deu_3:10), about 30 miles east of the Sea of Tiberias, and 30 miles west of the Ḥaurân range.

The Cambridge Bible for Schools and Colleges (gen. ed. J. J. S. Perowne; Cambridge University Press, 1878–1918) — public domain. Text from a community e-Sword module.

Fear him not; a necessary caution, for he was a great giant, Deu 3:11, likely to strike them with terror.

Matthew Poole's English Annotations on the Holy Bible (1683–1685) — public domain. Text from a community e-Sword/MySword module.

34. I have delivered — The promise is strengthened by the past tense. Israel’s fidelity is the implied condition. Israel’s unbelief would have lost the battle.

Daniel D. Whedon (gen. ed.), Commentary on the Old and New Testaments (1874–1909) — public domain. Text from a community e-Sword module.

Fear him not. He might well have been formidable, not only on account of his size, (cf. Deu_1:28 Deu_3:11 1Sa_17:11) but from the formidable nature of those walled cities which are still a wonder to all that see them.

The Pulpit Commentary (1880–1919), ed. H.D.M. Spence-Jones & Joseph S. Exell — public domain. Text from a community e-Sword module.

אל תירא אתו FEAR HIM NOT — God said this concerning Og but not about Sihon (cf v. 23), because Moses feared to wage battle, perhaps the merit of Abraham with whom Og had been associated would stand up (i.e., be an advocate) for him, as it is said, (Genesis 14:13) “And the one who escaped came [and told it to Abraham]” — this was Og who had escaped from the Rephaim whom Chedoladmar and his allies had smitten in Ashoreth Karnaim (Genesis 14:5), as it is said, (Deuteronomy 3:11). "For only Og king of Bashan was left of the remnant of the Rephaim" (cf. Midrash Tanchuma, Chukat 25, Niddah 61a).

Rashi on the Tanakh — English translations: “The Judaica Press complete Tanach with Rashi, translated by A. J. Rosenberg” (CC BY 4.0); “Pentateuch with Rashi's commentary by M. Rosenbaum and A.M. Silbermann, 1929-1934” (public domain); “The Metsudah Tanach series, Lakewood, N.J” (CC BY 4.0); and “The Book of Joshua, Metsudah Publications, 1997” (CC BY 4.0). Text via Sefaria.

FEAR HIM [Og] NOT. “For Moses was afraid [to wage war against Og] in case the merit of Abraham [whom Og had helped] would stand him in stead, for it is said about him, And there came ‘hapalit’ (one that had escaped) and told Abram the Hebrew, this being Og who had escaped from the Rephaim whom Amraphel and his allies had defeated at Ashteroth-karnaim.” This is Rashi’s language, based on the words of our Rabbis. 25; Bamidbar Rabbah 19:19. Here too the Rabbis were induced to make this comment because they knew that Moses our teacher would not have been afraid of an arm of flesh, for with him was the Eternal our G-d, and all the nations are as nothing before Him; they are accounted by Him as things of nought, and vanity. [Furthermore], it was he [Moses himself] who admonished Israel: fear not, nor be dismayed on account of them, and who criticized them for being afraid of them, as it is said in connection with the [affair of the] spies, Then I said unto you: ‘Dread not, neither be afraid of them. The Eternal your G-d, Who goeth before you, He shall fight for you.’, 1:29-30. Therefore [we must say] that Moses was afraid [of Og] because he knew of his merit [in having helped Abraham].In accordance with the plain meaning of Scripture, Moses had not intended now to give Israel the land of Sihon and Og as an inheritance, as I have explained. But Sihon had gone out against Israel into the wilderness, Verse 23. and had fought them against their will [in spite of their desire for peace]. Then G-d informed [Moses], Behold, I have begun to deliver up Sihon and his land before thee; begin to possess his land, for here began the conquest of the seven nations [who inhabited the Land of Israel]. But Og [nonetheless] mobilized all his forces at Edrei, which was a city at the end of his border, and Israel could have turned away from him just as they had turned away from Esau [i.e., Edom]. Therefore G-d told Moses, “Fear him not; go to him and contend with him in battle, for I have delivered him into thy hand.” And in Bamidbar Sinai Rabbah I have seen [the following text] “Why was Moses afraid [of Og]? He said: Perhaps Israel committed a trespass in the war against Sihon, [by taking of the spoil for themselves], or maybe they have become defiled by sins.” This is a completely homiletic exposition. And indeed all righteous people have this fear [that they might have sinned in error], and this [fear] likewise occurred [in the case] of Joshua [about whom it says that G-d told him, Fear not, neither be thou dismayed]. Balak

Ramban (Nachmanides) on the Tanakh — English translation: “Commentary on the Torah by Ramban (Nachmanides). Translated and annotated by Charles B. Chavel. New York, Shilo Pub. House, 1971-1976” (CC BY 4.0). Text via Sefaria.