Avot304

21:
The Shamir. We come now to the seventh of the ten things which were created on Erev Shabbat at twilight. Actually, all the remaining items belong together: the Shamir, the letters, the writing and the tablets. This is because they are all connected with the same miraculous event.

22:
The term shamir first occurs in the bible. The prophet Jeremiah is appalled at the intransigence of his contemporaries:

Here, the Hebrew shamir is rendered 'adamant'. The prophet elegizes that his people have hearts of stone, but their guilt (of the sin of idolatry) is indelibly engraved on their stone hearts by an iron pen which has a point of adamant. Adamant is is substance which is so hard that it will penetrate stone.

Yet again, when God wants to assure the prophet Ezekiel that his opponents will not be able to harm him he is told that

This substance, this 'adamant', is so miraculous in its qualities of hardness that it must have been created "on Erev Shabbat at twilight".

23:
When King Solomon built the first Bet Mikdash we are told that

Now, if no iron tool was used in the building of the Temple how were the stones hewn for the building? Of course, Solomon used the shamir which had been created "on Erev Shabbat at twilight". The Tosefta [Sotah 15:1] tells us that this shamir implement ceased to exist with the destruction of the Bet Mikdash.

24:
We must now turn our attention to the quadruplet "the Shamir, the letters, the writing and the tablets". Most scholars think that "the writing" refers to the art of writing. In other words, the ability to write down words was a miracle that was built into creation. However, this seems to me to be problematic, since writing was an art that was known to much of mankind from earliest times; and even before the giving of the Torah Moses was instructed to write down God's eternal enmity towards Amalek [Exodus 17:14]. It seems more reasonable to understand the "writing" in our present context as referring to the miraculous way in which writing appeared on the two tablets of stone which Moses brought down from the summit of Sinai.

To be continued.

In Avot 301 I pondered why the sages viewed the rainbow that appeared in the sky after the flood in the time of Noah as being miraculous. I mused that this may have been because it seemed to be ethereal; or possibly the sages do not see every rainbow as being 'beyond nature', but only the one that was seen in the sky by Noah.

Michal Roth writes:

I can see why the sages perceived the rainbow that Noah saw as a miracle. Rainbows appear when there are drops of water in the air, but this rainbow appeared after the rain, which had been coming down for forty days and nights, had stopped. The air was freshly out of raindrops and yet a rainbow appeared – that was the miracle!