It is written, "Do not rob the poor" (Proverbs 22:22). By what is a poor man's name called before you? A rich man's name is called after his gold and silver and precious stones and pearls; but by what is a poor man's name called before you? After his son. How so? His son stands and reads from the Torah, and one asks, "Whose son is this?" and the answer is, "The son of so-and-so, a poor man." And so it says, "For the LORD will plead their cause and rob of life those who rob them." Once I was passing from place to place and I met a certain old man. I said to him, "Master, why are the householders of Israel held back from having children?" I said to him: My son, because the Holy One, blessed be He, loves them with a complete love and rejoices in them, and refines them so that they will multiply mercy-pleas before Him. Go and learn from Abraham and Sarah, who were childless of Isaac for seventy-five years and multiplied prayers until Isaac came and they rejoiced in him. Go and learn from Rebecca, who was barren twenty years and multiplied prayers until Jacob came and they rejoiced in him. Go and learn from Rachel, who was barren fourteen years before her two children and multiplied prayers until both came and she rejoiced in them. Go and learn from Hannah, who was barren nineteen years and six months until Samuel came and she rejoiced in him. "And Sarai, Abram's wife, had borne him no children." "A woman of valor who can find, her worth is far above pearls" (Proverbs 31:10). What is "her worth"? Her conceiving, as you say "your birth and your nativity." Abraham was a year older than Nahor, and Nahor a year older than Haran; thus Abraham was two years older than Haran, one year for Milcah's gestation and one for Iscah's. Haran fathered children at six years old [text uncertain], and Abraham fathered none. "And Sarai, Abram's wife, had borne him no children." Rabbi Yehudah says: to him she had not borne, but had she married another she would have borne. Rabbi Nehemiah says: neither to him nor to another. How then does Rabbi Nehemiah uphold "she had borne him no children"? She had no womb at all, but God fashioned one. And she had a Egyptian handmaid, a melog-slave, for whose maintenance he was responsible and whom he was not permitted to sell. Rabbi Shimon ben Yochai said: Hagar was Pharaoh's daughter. When Pharaoh saw the wonders done for Sarah in his house, he gave her his daughter, saying, "Better that my daughter be a handmaid in this house than a noblewoman in another house." This is what is written, "and she had an Egyptian handmaid whose name was Hagar," that is, "here is your reward." Abimelech too, when he saw the miracles done for Sarah in his house, gave her his daughter as a handmaid, saying, "Better that my daughter be a handmaid in this house than a noblewoman in another house." This is what is written, "Kings' daughters are among your honored women" (Psalms 45:10), the daughters of kings, "the queen stands at your right hand" -- this is Sarah.
Why the Holy One Keeps the Beloved Barren Before Granting Them Children
Yalkut Shimoni on Torah 78:3
כְּתִיב (משלי כב, כב) "אַל תִּגְזֹל דָּל" וְגוֹ', עָנִי בַּמֶּה יִקָּרֵא שְׁמוֹ לְפָנֶיךָ, עָשִׁיר יִקָּרֵא שְׁמוֹ עַל שֵׁם זָהָב וְכֶסֶף וַאֲבָנִים טוֹבוֹת וּמַרְגָּלִיּוֹת אֲבָל עָנִי בַּמֶּה יִקָּרֵא שְׁמוֹ לְפָנֶיךָ, עַל שֵׁם בְּנוֹ, כֵּיצַד, עָמַד בְּנוֹ וְקָרָא בַּתּוֹרָה אוֹמֵר בֶּן מִי הוּא זֶה, אוֹמֵר בֶּן פְּלוֹנִי עָנִי הוּא וְכֵן הוּא אוֹמֵר, "כִּי ה' יָרִיב רִיבָם וְקָבַע אֶת קוֹבְעֵיהֶם נָפֶשׁ". פַּעַם אַחַת הָיִיתִי עוֹבֵר מִמָּקוֹם לְמָקוֹם, מָצָאתִי זָקֵן אֶחָד, אָמַרְתִּי לוֹ, רַבִּי, מִפְּנֵי מַה בַּעֲלֵי בָּתִים שֶׁבְּיִשְׂרָאֵל נֶעֱצָרִים עַל הַבָּנִים מִהְיוֹת לָהֶם. אָמַרְתִּי לוֹ, בְּנִי, מִפְּנֵי שֶׁהַקָּדוֹשׁ בָּרוּךְ הוּא אוֹהֲבָן אַהֲבָה גְּמוּרָה וְשָׂמֵחַ (בּוֹ) [בָּהֶם]. וּמְצָרְפָן בָּהֶן כְּדֵי שֶׁיַּרְבּוּ רַחֲמִים לְפָנָיו, צֵא וּלְמַד מֵאַבְרָהָם וְשָׁרָה שֶׁהָיוּ עֲקָרִים מִיִּצְחָק שִׁבְעִים וְחָמֵשׁ שָׁנָה וְהִרְבּוּ רַחֲמִים עַד שֶׁבָּא יִצְחָק וְשָׂמְחוּ בּוֹ, צֵא וּלְמַד מֵרִבְקָה שֶׁהָיְתָה עֲקָרָה עֶשְׂרִים שָׁנָה, וְהִרְבְּתָה רַחֲמִים, עַד שֶׁבָּא יַעֲקֹב וְשָׂמְחוּ בּוֹ. צֵא וּלְמַד מֵרָחֵל שֶׁהָיְתָה עֲקָרָה אַרְבַּע עֶשְׂרֵה שָׁנָה מִשְּׁנֵי יְלָדִים וְהִרְבְּתָה רַחֲמִים, עַד שֶׁבָּאוּ שְׁנֵיהֶן וְשָׂמְחָה בָּהֶן. צֵא וּלְמַד מֵחַנָּה שֶׁהָיְתָה עֲקָרָה תְּשַׁע עֶשְׂרֵה שָׁנָה וְשִׁשָּׁה חֳדָשִׁים, עַד שֶׁבָּא שְׁמוּאֵל וְשָׂמְחָה בּוֹ. וְשָׁרַי אֵשֶׁת אַבְרָם לֹא יָלְדָה לוֹ. (משלי לא, י) "אֵשֶׁת חַיִל מִי יִמְצָא וְרָחוֹק מִפְּנִינִים מִכְרָהּ". מַהוּ "מִכְרָהּ" עִבּוּרָה כְּמָה דְּאַתְּ אָמַר "מְכֹרֹתַיִךְ וּמֹלְדֹתַיִךְ". אַבְרָהָם הָיָה גָּדוֹל מִנָּחוֹר שָׁנָה נָחוֹר גָּדוֹל מֵהָרָן שָׁנָה. [נִמְצָא] אַבְרָהָם גָּדוֹל מֵהָרָן שְׁתֵּי שָׁנִים, [שָׁנָה] לְעִבּוּרָהּ שֶׁל מִלְכָּה, וְשָׁנָה לְעִבּוּרָהּ שֶׁל יִסְכָּה. הָרָן מוֹלִיד לְשֵׁשׁ וְאַבְרָהָם אֵינוֹ מוֹלִיד. וְשָׂרַי אֵשֶׁת אַבְרָם לֹא יָלְדָה לוֹ. רַבִּי יְהוּדָה אוֹמֵר, לוֹ לֹא יָלְדָה, אִלּוּ נִשֵּׂאת לְאַחֵר יָלְדָה רַבִּי נְחֶמְיָה אוֹמֵר, לֹא לוֹ וְלֹא לְאַחֵר וּמַה מְקַיֵּם רַבִּי נֶחֶמְיָה (אוֹמֵר) לֹא יָלְדָה לוֹ, אֶלָּא לוֹ וְלָהּ וְלָהּ שִׁפְחָה מִצְרִית. שִׁפְחַת מִלוּג הָיְתָה, וְהָיָה חַיָּב בִּמְזוֹנוֹתֶיהָ, וְלֹא הָיָה רַשָּׁאִי לְמָכְרָהּ. בָּעוּ מֵרֵישׁ לָקִישׁ, מַהוּ דְּתַנְיָא מִלּוּג אָמַר לֵיהּ, כַּמָּה דְּאַתְּ אָמַר מְלוֹג מְלוֹג. אָמַר רַבִּי שִׁמְעוֹן בֶּן יוֹחָאי, הָגָר בִּתּוֹ שֶׁל פַּרְעֹה הָיְתָה, כֵּיוָן שֶׁרָאָה פַּרְעֹה מַעֲשִׂים שֶׁנַּעֲשׂוּ לְשָׂרָה בְּבֵיתוֹ, נָתַן לָה בִּתּוֹ. אָמַר, מוּטָב שֶׁתְּהֵא בִּתִּי שִׁפְחָה בְּבַיִת זֶה, וְלֹא תְּהֵא מַטְרוֹנִיתָא בְּבַיִת אַחֵר. הֲדָא הוּא דִּכְתִיב, וְלָהּ שִׁפְחָה מִצְרִית וּשְׁמָהּ הָגָר הָא אַגְרֵיךְ אַף אֲבִימֶלֶךְ כֵּיוָן שֶׁרָאָה נִסִּים שֶׁנַּעֲשׂוּ לְשָׂרָה בְּבֵיתוֹ נָתַן לָה בִּתּוֹ לְשִׁפְחָה. אָמַר, מוּטָב שֶׁתְּהֵא בִּתִּי שִׁפְחָה בְּבַיִת זֶה וְלֹא תְּהֵא מַטְרוֹנִיתָא בְּבַיִת אַחֵר. הֲדָא הוּא דִּכְתִיב, (תהלים מה, י) "בְּנוֹת מְלָכִים בִּיקְרוֹתֶיךָ" בְּנוֹתֵיהֶם שֶׁל מְלָכִים, "נִצְּבָה שֵׁגָל לִימִינְךָ", זוֹ שָׂרָה.