Musar for Pirkei Avot 5:6
עֲשָׂרָה דְבָרִים נִבְרְאוּ בְּעֶרֶב שַׁבָּת בֵּין הַשְּׁמָשׁוֹת, וְאֵלּוּ הֵן, פִּי הָאָרֶץ, וּפִי הַבְּאֵר, וּפִי הָאָתוֹן, וְהַקֶּשֶׁת, וְהַמָּן, וְהַמַּטֶּה, וְהַשָּׁמִיר, וְהַכְּתָב, וְהַמִּכְתָּב, וְהַלּוּחוֹת. וְיֵשׁ אוֹמְרִים, אַף הַמַּזִּיקִין, וּקְבוּרָתוֹ שֶׁל משֶׁה, וְאֵילוֹ שֶׁל אַבְרָהָם אָבִינוּ. וְיֵשׁ אוֹמְרִים, אַף צְבָת בִּצְבָת עֲשׂוּיָה:
Ten things were created on the eve of Sabbath at twilight, [i.e., on the eve of the Sabbath of the creation, before its completion]: the mouth of the earth [to swallow up Korach and his congregation], the mouth of the well [of Miriam, which accompanied Israel in the desert in all of its journeyings. (Some say that it opened its mouth and sang (Numbers 21:17): "Arise, O, Well, sing to her!"], the mouth of [Bilam's] ass, [At twilight it was decreed that it speak with Bilam], the rainbow, [as a sign of the covenant that a second flood would not occur], the manna [that descended for Israel forty years in the desert], the [sapphire] staff, [with which the signs were performed], the shamir [a type of worm the size of a barley grain. When they held it over the stones figured with ink, they split of themselves. With it they formed the stones of the ephod and the choshen, viz. (Exodus 28:20): "With their (exact) fillings"], the writing, [the form of the letters carved on the tablets], the inscription, [their being read from all four sides], and the tablets. [They were of sapphire. Their length was six (ells); their breadth was six, and their thickness was three, like one stone, whose length and breadth and thickness are uniform. It was divided into two. And they were rolled and hewn from the solar orb.] Some say, also the mazikkin, [the demons. After the Holy One Blessed be He created Adam and Eve, He was preoccupied with their creation, and when He created their spirits, He had not created their bodies by the advent of the Sabbath, so that they remained spirits without bodies], and the grave of Moses, and the ram of our father Abraham. [It was decreed at twilight that it be caught in the thicket by its horns]. Some say: Also the tongs, made from a tongs. [The tongs is made only from another tongs. And who made the first tongs? Perforce we must say that it was made by itself (i.e., by Heaven); and it was created at twilight. This is rejected by the Gemara (Pesachim 54a), which states that the first tongs could have been cast in a mold and forged at once.]