In our Torah portion this week while Jacob is blessing his grandchildren Ephraim and Manasseh he says:
The angel who has redeemed me from all evil, bless the boys; and in them let my name be carried on, and the name of my fathers Abraham and Isaac; and let them grow into a multitude in the midst of the earth. (Genesis 48:16)
The phrase “Let them grow into a multitude in the midst of the earth” can be better translated as “Let them increase like fish in the land.” If this is correct, this seems like a strange blessing. Yes, fish multiply and grow abundant, but so do many other species. And why say “in the land” when fish live in the water?
Rabbi Avraham Yitzchak HaKohen Kook, the first chief rabbi of modern Israel, offers us a unique interpretation of this verse. First, he brings in a passage from the Talmud:
Just as the fishes [dagim] in the sea are covered by the waters and the evil eye has no power over them so the evil eye has no power over the seed of Joseph. (b.B’rachot 55b)
What does this mean? How is Joseph immune to the evil eye (i.e., greed) like fish? Rav Kook answers:
We explained previously that the Evil Eye is an example of hidden influences that exist between souls. An environment of jealousy and hatred can poison not only the atmosphere but also the soul against whom they are directed. This, however, is only true for weaker souls that are easily influenced. The Evil Eye can only harm those whose sense of self-worth is not fully developed, people who need to live their lives in a way that meets the approval of foreign “eyes.” But if we are secure within ourselves, and our life is focused on our inner truths, then we will not be susceptible to the Evil Eye of those around us. The Evil Eye has no power over those whose robust sense of self-esteem does not let others dictate what is important and worthwhile. 
And how is this illustrated in fish?
Fish are not concerned with envious eyes above the water. They live in their own world below the surface, a secluded realm that determines the direction of their lives. Like the fish, Joseph remained faithful to his inner convictions, despite the external pressures and influences of his roller-coaster life. Family estrangement, a foreign land, a foreign culture, temptations, slavery, and imprisonment—none of these succeeded in leading Joseph astray. Even when he needed to contend with the hardest test of all—the incredible success, wealth, and power as Egyptian viceroy—Joseph was steadfast in his beliefs and inner convictions. Joseph remained true to his own inner world, despite his active participation in a vastly different outer world. Just like a “fish in the land.” 
Rav Kook teaches us that Jacob blesses his grandchildren and their descendants so that they should be free from the grips of envy and greed, which are the root of so many of sins. Even, when they are out of their element, like a fish out of water, they should not be distracted by the nation’s ways around them but focus on the service of HaShem and his Torah. This reminds us of the Master’s Yeshua’s words about the seeds that fell upon the thorns:
They are those who hear the word, but the cares of the world and the deceitfulness of riches and the desires for other things enter in and choke the word, and it proves unfruitful. (Mark 4:18-19)
Yeshua, too, repeatedly warns us not to be caught up in the greed and lust for riches that is so prevalent in the world. Is it a coincidence as well that one of the earliest symbols of the believers was a fish? May we, as disciples of the Master, increase as fish upon the earth.
- Rabbi Avraham Yitzchak HaKohen Kook, “Vayechi: Fishy Blessing,” n.p. [cited 8 December 2017]. Online: http://ravkooktorah.org/VAYEHI59.htm
Source: First Fruits of Zion