The beginning of the portion of Toldot recounts the struggle of Isaac and Rebecca to have children: “And Isaac prayed to God opposite his wife because she was barren, and the Lord accepted his prayer, and Rebecca his wife conceived” (Genesis 25:21). One tradition states that Isaac and Rebecca stood on opposite sides of the room yet prayed together for children.
It is thus interesting to note that in the Shabbat prayers according to Nusach Sefard (and in Nusach Ashkenaz on Rosh Hashanah and Yom Kippur) the names of Isaac and Rebecca appear in an acrostic encoded in the Shochen Ad prayer in the following manner: After the introductory lines, there are four lines of three words each. The second word in each of these lines begins with the Hebrew letters that spell יצחק (Yitzchak), while the third letters of each of the third words in order spell the name רבקה (Rivkah). This alludes to how Isaac and Rebecca prayed across from each other to have children:
בְּפִי יְשָׁרִים תִּתְרוֹמַם
וּבְשִׂפְתֵי צַדִּיקִים תִּתְבָּרַךְ
וּבִלְשוֹן חֲסִידִים תִּתְקַדַּשׁ
וּבְקֶרֶב קְדוֹשִׁים תִּתְהַלָּל
