In the beginning of Parshas Toldos, we learn of the struggles of Yitzchak and Rivka to bear offspring.  The Torah tells us that both Yitzchak and Rikva davened that offspring be granted to them. וַיֶּעְתַּ֨ר יִצְחָ֤ק לַֽה֙ לְנֹ֣כַח אִשְׁתּ֔וֹ כִּ֥י עֲקָרָ֖ה הִ֑וא וַיֵּעָ֤תֶר לוֹ֙ ה וַתַּ֖הַר...