Chasidut zu Bereschit 50:23

There is another approach to this word found in the ‎explanation by Nachmanides, (last section) on ‎פרשת בשלח‎, on ‎Exodus 17,9 according to which whatever Moses and Joshua had ‎done in their time would be re-enacted by the prophet Elijah and ‎the messiah, descended from Joseph in due course. According to ‎our tradition the messiah from the house of David will reveal ‎himself only after the death of the messiah from the house of ‎Joseph., so that the process of redemption will begin with the ‎appearance of the prophet Elijah, followed by the messiah from ‎the house of Joseph, and will be completed with the redemption ‎under the messiah from the house of David. This trilogy is alluded ‎to by the shalshelet above the word ‎וימאן‎. When Joseph ‎reminded himself of this sequence, he was reinforced in his ‎determination not to give in to the allure of Potiphar’s wife. This ‎is also why the Torah reports in Genesis 50,23 ‎וירא יוסף לאפרים בני ‏שלשים‎, “Joseph was privileged to see a third generation of ‎Ephrayim.” The final letter ‎ם‎ at the end of this verse is ‎mysterious. [We would have expected the letter ‎י‎ instead, ‎indicating the ordinal number “third.” Ed.] This letter is an ‎allusion to Isaiah 9,6 where the word ‎לםרבה המשרה‎, is written ‎with the final letter ‎ם‎ at the beginning of the word. According to ‎our tradition (Sanhedrin 94) the final letter ‎ם‎ there is an ‎allusion to the final letter ‎ם‎ in the word ‎אפרים‎, a hint that the ‎messiah from the house of Joseph will be a descendant of ‎Ephrayim. (Compare Bamidbar Rabbah 14,2. Zohar II ‎‎100, also elaborates on the subject of the messiah from the house ‎of David following the messiah from the house of Joseph when ‎discussing aspects of the levirate marriage.)‎