Why did Moses have a ten-cubit-long axe?

Question

The Talmud in Berachot 54b relates the following tale:

אבן שבקש עוג מלך הבשן לזרוק על ישראל גמרא גמירי לה אמר מחנה ישראל כמה הוי תלתא פרסי איזיל ואיעקר טורא בר תלתא פרסי ואישדי עלייהו ואיקטלינהו אזל עקר טורא בר תלתא פרסי ואייתי על רישיה ואייתי קודשא בריך הוא עליה קמצי ונקבוה ונחית בצואריה הוה בעי למשלפה משכי שיניה להאי גיסא ולהאי גיסא ולא מצי למשלפה והיינו דכתיב שני רשעים שברת וכדר' שמעון בן לקיש דא"ר שמעון בן לקיש מאי דכתיב שני רשעים שברת אל תקרי שברת אלא שרבבת משה כמה הוה עשר אמות שקיל נרגא בר עשר אמין שוור עשר אמין ומחייה בקרסוליה וקטליה

'The stone which Og, king of Bashan wanted to throw at Israel'. This has been handed down by tradition. He said: How large is the camp of Israel? Three parasangs. I will go and uproot a mountain of the size of three parasangs and cast it upon them and kill them. He went and uprooted a mountain of the size of three parasangs and carried it on his head. But the Holy One, blessed be He, sent ants which bored a hole in it, so that it sank around his neck. He tried to pull it off, but his teeth projected on each side, and he could not pull it off. This is referred to in the text, Thou hast broken the teeth of the wicked, as explained by R Simeon b. Lakish. For R. Simeon b. Lakish said: What is the meaning of the text, Thou hast broken the teeth of the wicked? Do not read, shibbarta [Thou hast broken], but shirbabta [Thou hast lengthened]. The height of Moses was ten cubits. He took an axe ten cubits long, leapt ten cubits into the air, and struck him on his ankle and killed him.

(Soncino translation)

A ten-cubit-long axe is not exactly a common household item. So I am wondering how Moses just happened to have such an axe? Was this just a random coincidence? Did he always have the axe for some reason? Did he fashion the axe at the moment in order to fight Og? Did the axe miraculously appear? Some other option?

Note: Obviously this question only makes sense if the Talmudic tale is to be taken literally. So I would not consider an answer that challenges the literalness of the tale as a valid answer to this question.

Answer 1

I don’t know for sure, since it isn't clarified further by the Midrash or other parallel Midrashim that I found. However, here are a couple of related points, which may qualify as an answer:

In Sefer Kasa Depischa, he suggests that this "Narga" was actually Moshe's staff, and proceeds to ask a question based on that. If so, he had his staff with him regularly, and it would make for a good weapon:

However, from the language of Targum Pseudo-Yonasan to Bamidbar 21:35, it is clear he had to fetch the weapon from elsewhere:

אזל משה ונסב נרגא