Text 10
And he made the washstand of copper and its base of copper from the mirrors of the women who had set up the legions, who congregated at the entrance of the Tent of Meeting.
Shemos, 38:8
Rashi’s commentary on that particular verse describes (based on the Medrash) how Moshe had originally opposed using these mirrors in the construction of the Mishkan, and that G-d specifically instructed him to do so.
Text 11
The Israelite women owned mirrors, which they would look into when they adorned themselves. Even these [mirrors] they did not hold back from bringing as a contribution toward the Mishkan, but Moshe despised them because they were made for temptation [i.e., to inspire lustful thoughts]. The Holy One, blessed is He, said to him, “Accept [them], for these are more precious to Me than anything because through them the women set up many legions [i.e., through the children they gave birth to] in Egypt.” When their husbands were weary from back-breaking labor, they [the women] would go and bring them food and drink and give them to eat. Then they [the women] would take the mirrors and each one would see herself with her husband in the mirror, and she would seduce him with words, saying, “I am more beautiful than you.” And in this way they aroused their husbands’ desire and would copulate with them, conceiving and giving birth there.
Rashi, ibid
Moshe despised the mirrors, as they are a tool for temptation. G-d, however, loved them, as they were used to create the Jewish people.
From one angle, the mirrors served a lowly function as a tool for arousing desire, and from another, they were so valued by G-d, that he treasured them above all else.
This dichotomy that on one hand, they were a tool for negativity and on the other, they were especially precious, is expressed in the kiyor as well. While it is the lowest of the vessels, there is also an element within it, in which it is the highest, and expressive of Moshe.
