(Exodus 1:16) "And he said: When you deliver the Hebrew women, look upon the birthstool [ovnayim]." He handed them a great sign, as it is written, "And I went down to the potter's house, and behold, he was doing work upon the stones [ovnayim]" (Jeremiah 18:3). He said to them: Just as this potter has one thigh on this side and one thigh on that side and the block in the middle, so too a woman has one thigh on this side and one thigh on that side and the child in the middle. And there are those who say: at the moment she crouches to give birth, her thighs grow cold like stones. "If it is a son, you shall put him to death" (Exodus 1:16). He handed them a great sign: a son's face is downward, a daughter's face is upward. "And the midwives feared God and did not do as he spoke to them" (Exodus 1:17). It should have said "to them [lahen]." Rather, this teaches that he demanded of them a matter of transgression, and they were not taken. "And they did not do as the king of Egypt spoke to them" [interpreted as: he solicited them and they did not submit].
Pharaoh's Sign at the Birthstool and the Midwives Who Refused
Yalkut Shimoni on Torah 164:7
(שמות א טז) וַיֹּאמֶר בְּיַלֶּדְכֶן אֶת הָעִבְרִיּוֹת וּרְאִיתֶן עַל הָאָבְנָיִם, סִימָן גָּדוֹל מָסַר לָהֶן, דִּכְתִיב (ירמיה יח, ג) "וָאֵרֵד בֵּית הַיּוֹצֵר וְהִנֵה הוּא עֹשֶׂה מְלָאכָה עַל הָאָבְנָיִם", אָמַר לָהֶן מָה יוֹצֵר זֶה יָרֵךְ מִכָּאן וְיָרֵךְ מִכָּאן וְסַדָּן בָּאֶמְצַע, אַף אִשָּׁה יָרֵךְ מִכָּאן וְיָרֵךְ מִכָּאן וְהַוָּלָד בָּאֶמְצַע. וְאִית דְּאָמְרֵי בְּשָׁעָה שֶׁכּוֹרַעַת לֵילֵד יַרְכוֹתֶיהָ מִצְטַנְּנוֹת כָּאֲבָנִים. אִם בֵּן הוּא וַהֲמִתֶּן אֹתוֹ, סִמָּן גָּדוֹל מָסַר לָהֶם, בֵּן פָּנָיו לְמַטָּה, בַּת פָּנֶיהָ לְמַעְלָה. (שמות א יז) וַתִּירֶאןָ הַמְיַלְּדֹת אֶת הָאֱלֹהִים וְלֹא עָשׂוּ כַּאֲשֶׁר דִּבֶּר אֲלֵיהֶן, 'לָהֶן' מִבָּעֵי' לֵיהּ, אֶלָּא מְלַמֵּד שֶׁתְּבָעָן לִדְבַר עֲבֵרָה, וְאֵינָן נִתְבָּעוֹת.