Rabbi Eliezer says: Five letters that are doubled among all the letters in the Torah are all for the mystery of redemptions. Kaf-Kaf (the final form): Abraham our father was redeemed from Ur of the Chaldees, as it is said, "Go forth (lekh lekha) from your land" (Genesis 12:1). Mem-Mem (the final form): through it Isaac our father was redeemed from the hand of the Philistines. Nun-Nun (the final form): through it Jacob our father was redeemed. Pe-Pe (the final form): through it our fathers were redeemed from Egypt, as it is said, "I have surely remembered (pakod pakadti)" (Exodus 3:16). Tzadi-Tzadi (the final form): through it the Holy One, blessed be He, is destined to redeem Israel from the subjugation of the four kingdoms. And all of them were handed over only to Abraham our father, and Abraham handed them on to Isaac, and Isaac handed them on to Jacob, and Jacob handed the mystery of redemption on to Joseph, as it is said, "And God will surely remember (pakod yifkod) you" (Genesis 50:24). And Joseph his son handed the mystery of redemption on to his brothers, and Asher handed the mystery of redemption on to Serah his daughter.
The Secret Of The Redeemer
Pirkei DeRabbi Eliezer 48
רַבִּי אֱלִיעֶזֶר אוֹמֵר: חֲמִשָּׁה אוֹתִיּוֹת שֶׁנִּכְפְּלוּ בְּכָל הָאוֹתִיּוֹת שֶׁבַּתּוֹרָה כֻּלָּם לְסוֹד גְּאֻלּוֹת. כָּ״ף כָּ״ף – אַבְרָהָם אָבִינוּ נִגְאַל מֵאוּר כַּשְׂדִּים, שֶׁנֶּאֱמַר ״לֶךְ לְךָ מֵאַרְצְךָ״. מֵ״ם מֵ״ם – נִגְאַל בּוֹ יִצְחָק אָבִינוּ מִיַּד פְּלִשְׁתִּים. נוּ״ן נוּ״ן – נִגְאַל בּוֹ יַעֲקֹב אָבִינוּ. פֵּ״א פֵּ״א – בּוֹ נִגְאֲלוּ אֲבוֹתֵינוּ מִמִּצְרַיִם, שֶׁנֶּאֱמַר ״פָּקֹד פָּקַדְתִּי״. צָדִ״י צָדִ״י – בּוֹ עָתִיד הַקָּדוֹשׁ בָּרוּךְ הוּא לִגְאֹל אֶת יִשְׂרָאֵל מִשִּׁעְבּוּד אַרְבַּע מַלְכֻיּוֹת. וְכֻלָּם לֹא נִמְסְרוּ אֶלָּא לְאַבְרָהָם אָבִינוּ, וְאַבְרָהָם מְסָרָן לְיִצְחָק, וְיִצְחָק מְסָרָן לְיַעֲקֹב, וְיַעֲקֹב מָסַר סוֹד הַגְּאֻלָּה לְיוֹסֵף, שֶׁנֶּאֱמַר ״וֵאלֹהִים פָּקֹד יִפְקֹד אֶתְכֶם״. וְיוֹסֵף בְּנוֹ מָסַר סוֹד הַגְּאֻלָּה לְאֶחָיו, וַאֲשֶׁר מָסַר סוֹד הַגְּאֻלָּה לְסֶרַח בִּתּוֹ.