מדרש על מגילה 1:9

Rabbi Eliezer said: The five letters of the Torah, which alone of all the letters in the Torah are of double (shape), all appertain to the mystery of the Redemption. With "Khaph" "Khaph" our father Abraham was redeemed from Ur of the Chaldees, as it is said, (Lekh Lekha) "Get thee out of thy country, and from thy kindred… unto the land that I will shew thee" (Gen. 12:1). With "Mem" "Mem" our father Isaac was redeemed from the land of the Philistines, as it is said, "Go from us: for thou art much mightier (Memennu M'ôd) than we" (Gen. 26:16). With "Nun" "Nun" our father Jacob was redeemed from the hand of Esau, as it is said, "Deliver me, I pray thee, (Hazilêne na) from the hand of my brother, from the hand of Esau" (Gen. 32:11). With "Pê" "Pê" Israel was redeemed from Egypt, as it is said, "I have surely visited you, (Paḳôd Paḳadti) and (seen) that which is done to you in Egypt, and I have said, I will bring you up out of the affliction of Egypt" (Ex. 3:16, 17). With "Zaddi" "Zaddi" the Holy One, blessed be He, in the future will redeem Israel from the oppression of the kingdoms, and He will say to them, I have caused a branch to spring forth for you, as it is said, "Behold, the man whose name is (Zemach) the Branch; and he shall grow up (yizmach) || out of his place, and he shall build the temple of the Lord" (Zech. 6:12). These letters were delivered only to our father Abraham. Our father Abraham delivered them to Isaac, and Isaac (delivered them) to Jacob, and Jacob delivered the mystery of the Redemption to Joseph, as it is said, "But God will surely visit (Paḳôd yiphḳôd) you" (Gen. 1. 24). Joseph his son delivered the secret of the Redemption to his brethren. Asher, the son of Jacob, delivered the mystery of the Redemption to Serach his daughter. When Moses and Aaron came to the elders of Israel and performed the signs in their sight, the elders of Israel went to Serach, the daughter of Asher, and they said to her: A certain man has come, and he has performed signs in our sight, thus and thus. She said to them: There is no reality in the signs. They said to her: He said "Paḳôd yiphḳôd"—"God will surely visit you" (ibid.). She said to them: He is the man who will redeem Israel in the future from Egypt, for thus did I hear, ("Paḳôd Paḳadti") "I have surely visited you" (Ex. 3:16). Forthwith the people believed in their God and in His messenger, as it is said, "And the people believed, and when they heard that the Lord had visited the children of Israel" (Ex. 4:31).