Beitzah 8A

בעפר תיחוח.

Here it is referring to loose earth that does not require further crushing.

והא קא עביד גומא! כדרבי אבא. דאמר רבי אבא: החופר גומא בשבת, ואינו צריך אלא לעפרה ⁠— פטור עליה.

The Talmud challenges this: But even in the case of loose earth, one makes a hole by the very act of removing the earth or the shovel from that place. The Talmud answers: This ruling is in accordance with the opinion of R' Abba, as R' Abba said: One who digs a hole on Shabbat, but he needs only its earth and has no interest in forming a pit, is exempt for that act. Since he has no interest in the hole, he is considered to have performed a destructive act, and the halakha is that one who commits a destructive act is not liable for the performance of prohibited labor on Shabbat and Festivals.

שאפר כירה מוכן הוא. אפר כירה מאן דכר שמיה? אמר רבה, הכי קאמר: ואפר כירה מוכן הוא.

§ The Mishnah states: That the ashes of a stove are prepared. The Talmud express puzzlement at this statement: The ashes of a stove, who mentioned anything about it? Why does the Mishnah suddenly speak about the ashes of a stove when it had not previously discussed or even mentioned them? Rabba said: This is what the tanna said: And the ashes of a stove are prepared. In other words, everyone agrees that in addition to prepared earth, the ashes of a stove are also considered prepared, and one may cover the blood with them. It is not necessary to prepare these ashes especially for this purpose the day before.

אמר רב יהודה אמר רב: לא שנו אלא שהוסק מערב יום טוב, אבל הוסק ביום טוב ⁠— אסור. ואם ראוי לצלות בו ביצה ⁠— מותר.

Rav Yehuda said that Rav said: They only taught that the ashes of a stove are considered prepared if the stove was ignited on the Festival eve, so that the ashes had already formed at the start of the Festival. However, if it was ignited on the Festival itself, the ashes are prohibited. And if the ashes are still hot and fit to roast an egg in them, they are not considered muktze, and therefore it is permitted to use them for covering as well.