When our ancestors were slaves, the Egyptians wanted to prevent the men from reproducing, in order to wipe Israel out. To that end, they weighed them down with backbreaking labor from dawn to dusk and forced them to sleep in the fields instead of returning home. To the men of Israel, the situation seemed hopeless; their wives would give up on them and instead cling to their Egyptian masters. How could a husband look his wife in the eye? He was supposed to shelter her, to protect her from tyrants and oppressors, to support her and defend her honor, to be a role model for their children. Instead, he was a lowly slave under the heel of his master. In order to spare himself further humiliation, he preferred not to attempt to approach his wife. He stifled his will to live. He did not want children, because he could not provide them with a decent future. When his wife approached him, he backed away, because he was afraid that she would want to leave him soon anyway. Under such circumstances, most women would feel slighted and would try to become the second wives of their Egyptian masters. And the people of Israel would have faced extinction.
Something else took place instead. The Sages recount:
In the merit of the righteous women of that generation, Israel was redeemed from Egypt. When the women went to draw water, the Holy One arranged for small fish to enter their pitchers, so they drew up pitchers half-full of water and half-full of fish. They then set two pots on the fire, one for hot water and the other for the fish. Then they carried these to their husbands in the fields, where they bathed them, massaged them with oil, and gave them food and drink. Then they coupled with them among the sheepfolds. (Sota 11b)
It was as if each woman said to her husband, “Although you are a contemptible slave in the eyes of the Egyptians, in my eyes you are precious and important. Just as I would greet you happily if you returned home from a respectable job, so I happily greet you now. I have come to the field to wash your feet, aching after a hard day’s work, and to massage your body, bruised from beatings, because you are my husband and my love.” A midrash relates similarly:
While they ate and drank, the women held up mirrors and looked into them together with their husbands. She would say, “I am more beautiful than you,” and he would respond, “I am better looking than you.” This stimulated their desire, and they would procreate; the Holy One would ensure immediate conception…. “The Israelites were fertile and prolific; they multiplied and increased very greatly” (Shemot 1:7)…. And all this proliferation was thanks to the mirrors. (Tanḥuma Pekudei §9).
“Once they became pregnant, they went home. When it was time for them to give birth, they went to the fields” (Sota 11b).
After the Jewish people left Egypt, received the Torah, and were commanded to erect the Mishkan, every Jew donated gold, silver, copper, expensive fabrics, and precious gems for its construction. The same women who had given birth in the fields asked themselves, “Do we have anything to contribute toward the building of the Mishkan?” They went home and returned carrying the same mirrors they had used to beautify themselves. Even though they treasured these mirrors, they volunteered to donate them out of their intense passion for sanctity. But Moshe was disgusted, because he felt that the whole point of mirrors was to arouse the evil inclination. Some say that he even became angry, telling the people around him in exaggerated fashion that these women deserve to have their legs broken with sticks for their audacity in bringing these mirrors for divine service. God responded to Moshe, “You disdain these mirrors?! These mirrors produced these multitudes in Egypt! Accept them, because they are more beloved to Me than all other donations. Take them and use them to make the copper laver and its base, with which the kohanim will sanctify themselves for divine service” (Tanḥuma Pekudei §9; Rashi on Shemot 38:8).
From this story we learn something wonderful: that there is nothing more pure and holy than unconditional, life-giving love. That is why it was specifically these mirrors that were used to make the laver from which the kohanim purified and sanctified themselves in preparation for Temple service.