Heaven and Earth, Earth and Heaven
Preceding the passing of his father Yaakov, Yosef brings his two sons Ephraim and Menashe to their venerated grandfather to receive his blessing. Although Menashe was Yosef's first-born (and as such he had the "official" claim to the more prestigious blessing); Yaakov, in his profound wisdom, recognized that it was Ephraim who should receive the greater bracha.
"And Yisrael sent his right [hand] and he placed it upon the head of Ephraim, and he was the young[er one], and his left [hand] upon the head of Menashe...and he placed Ephraim before Menashe (Beresheet. 48:14-20)."
The Torah describes the discussion that transpired between Yaakov and Yosef about this seemingly peculiar act. Yosef, of course, thought that his father (who at that point had lost his eyesight) was simply making a mistake and thus attempted to correct the error. However, "and his father refused and he said 'I know, my son, I know. He (Menashe) will also be to a nation and he will also become great, and however his younger brother will become greater than him... (Beresheet 48:19)."
The question that one may ask is what exactly is so significant about which hand he places on whose head? We would most likely assume that the relative power of a blessing depends solely on the content thereof and the intent behind it. Yet, the Torah is clearly teaching us the contrary; namely, that which hand he placed on which head did carry tremendous impact and significance as to the power of the respective blessings.
What we derive from this observation is one of the most fundamental principles of Torah and Judaism. Hashem created a universe that has a dual reality: the physical and material reality on the one hand, and the metaphysical/spiritual reality on the other. The human being is comprised of body and soul. One without the other is simply not a human being. As such, if we are to serve Hashem in the most optimal way it requires that we make usage of both facets of our existence together.
This is why placing the right hand on Ephraim's head made such a profound difference. By utilizing his stronger arm in blessing Ephraim, Yaakov was actually accessing a powerful, inner, spiritual strength within himself. It is not only that there exists a direct correlation between the physical and the spiritual, but that the principal way through which we can access and express our spiritual strength is by properly utilizing our physical capacities.
Shabbat Shalom, Rabbi Isaac Farhi