A recipe to avoid decline
ויברכם ביום ההוא לאמור בך יברך ישראל לאמר ישמך אלקים כאפרים וכמנשה וגו’
[Yaakov] blessed them on that day saying: “In you the Jewish people will bless, to say that Hashem should make you like Efraim and Menashe”…
Towards the end of Yaakov’s life, he blessed his children with various prophetic pronouncements. Before blessing his twelve children, he gave Yosef’s two sons their own special blessings. He informed them that the Jewish people will bless their own children to be like Efraim and Menashe. Indeed, the standard practice in a Jewish home is that Friday night the parents bless their sons to be like Efraim and Menashe. What’s the intent behind blessing our kids that they should be like Efraim and Menashe? What aspect did they have that we hope our children will share?
Rav Yaakov Weinberg zatzal suggested that the intent relates to yeridas hadoros. This Jewish concept is an observation that with every succeeding generation, there’s a certain decrease in spirituality and wisdom. Adam, the first Man, was directly created by G-d. Therefore, he was the most divine human. His children, although G-d was involved in their creation, had human parents. They’re one level removed from direct creation by Hashem. This continues as the generations progress. Similarly, the generation that was at Mount Sinai witnessed the greatest revelation of Hashem. They literally received the Torah from Him. Their children were one step removed from that. As such, every succeeding generation is one step further from Sinai, creating a decrease in their grasp of Torah.
One could argue that Efraim and Menashe are the only two brothers in history who were able to avoid yeridas hadoros. Yaakov didn’t look at them like they were his grandchildren. To him, they were on the same level as his own children. This is why he said that Efraim and Menashe would be like Reuven and Shimon. He observed that there was no decrease in spiritual stature from his children’s generation to their own. This is the blessing that we give our children, that they should be like Efraim and Menashe. They should see no spiritual decline from the generation that preceded them. How is it though that Efraim and Menashe avoided the reality of yeridas hadoros?
We can say that they learned it from their father, Yosef. At the beginning of the parsha, Yaakov instructed Yosef to ensure that he be buried in the land of Israel. Yosef agreed to the mission, by saying אעשה כדברך, I will do like your words. One interpretation of this phrase is that besides burying his father in the land of Israel, Yosef would ensure that he himself would also be buried there. This is because Yosef wanted to be exactly like his father Yaakov. Our Sages in fact tell us that everything that happened to Yaakov happened to Yaakov. The two shared similar destinies, and Yaakov had taught Yosef all that he knew. Yosef himself evaded yeridas hadoros, and was able to inculcate that ability into his children.
We see here a tremendous lesson in chinuch, raising our children and teaching our students. You can’t just talk the talk, you have to walk the walk. It’s one thing for us to want our children and students to be just like the generation that preceded them. But to actually make it a reality, desire alone may not be enough. The best way to teach a lesson or value to anyone is to live it yourself. If we ourselves strive to emulate the generation that preceded us, attaining heights beyond the norm for our generation, then that’s something we can properly pass on to the next generation. We see from Yosef that he was able to impart in his children amazing abilities, solely because he himself had attained them.
 Based on a shiur heard from Rabbi Yissocher Frand in 5779
 בך is hard to translate. It could mean here “in you”, “with you”, “through you”, but they’re all not the most grammatical
 Genesis 48:20
 This practice is first recorded by Sefer HaChaim Parnasa VeChalkala Chapter 6 § טעם למאמר בואו ונצא לקראת שבת כלה, written by the Maharal’s brother. The next source is Ma’avar Yabok Sifsei Rananos Chapter 43. The Kitzur Shulchan Aruch 131:16 and Chayei Adam 144:19 only mention this custom with regards to Yom Kippur evening. Credit to my brother in-law Rabbi Nachum Aharon haKohen Kutnowski for these sources
 The concept of yeridas hadoros appears in Shabbos 112b. See also Yevamos 39b. It is subsequently discussed in many sources. However, the earliest usage that I found of the specific phrase yeridas hadoros is in Rav Yaakov Emden’s Mor UKtziah § 88, from the 18th century
 Kiddushin 30b; Niddah 31a
 This Jewish concept is the exact opposite of Western Society’s weltanschauung or world view. The common conception is Man came from the animals, so every generation is one level less animal, and thus more advanced and wiser. This creates a certain apathy or disrespect for one’s elders, whereas Judaism due to its world view emphasizes respecting and honoring those who preceded us
 Genesis 48:5. See Ba’al HaTurim ad. loc., who points out that the numerical value of אפרים ומשנה is equal to ראובן ושמעון. However, upon inspection, one phrase’s numerical value is 732 and the other’s is 731. This is pointed out by HaRosh Al HaTorah ad. loc. This is fine though according to the rule in gematria known as im-hakolel, where numbers off by one are considered equivalent. The Benei Yissaschar brings in a few places (for example: Kislev UTeves 2:2, Chodesh Sivan 2:13) that this verse is actually the source for im-hakolel, since the verse says אפרים ומנשה כראובן ושמעון יהיו לי, meaning they will be equivalent. In the latter source he cites this from the Chida in Devash Lefi 3:14.
 I suppose one could ask then why we only wish this for our sons and not our daughters, who are blessed to be like Sarah, Rivka, Rochel, and Leah
 Genesis 47:30
 Da’as Zekeinim, Rabboseinu Ba’alei HaTosafos, Hadar Zekeinim and Rabbeinu Bachaye ad. loc., quoting a Midrash; Tur HaAroch ad. loc. without citation. See Torah Sheleimah ad. loc. § 128
 Bereishis Rabbah 84:6, Midrash Tanchuma Vayeishev § 1, ibid Miketz § 3, Tanchuma Yashan Vayeishev § 5, brought by Rashi to Genesis 37:2. See also Bamidbar Rabbah 14:5 and Torah Sheleimah to Genesis Chapter 37 § 25
 See Rashi, Ramban, and Targum Onkelos to Genesis 37:3 and Bereishis Rabbah 84:8