מוסר אויף בראשית 49:25

And from all of this awesome episode we can understand how much one must guard his tongue and his deeds. And also, from [the account of] Joseph, we can understand his holy trait, viz. (Ibid. 45:5): "And now, do not be grieved, and do not vex yourselves that you sold me here." And, similarly, at the end of the parshah (Ibid. 50:21): "And he comforted them and he spoke to their hearts." And witness further the greatness of Joseph, who did not tell his father what had been done to him, until it was revealed to him prophetically before his death, as it is written [(Jacob speaking)] (Ibid. 49:23): "They [the brothers] embittered him and they antagonized him and they hated him, etc." And, more than this, we find in the words of Chazal that Joseph took care not to be alone with his father, so that his brothers not suspect him of telling his father what he had suffered at their hands.

We may be able to answer a question raised in the Zohar on Genesis 49,25 where Jacob in his blessing for Joseph says: מאל , ואת שדי ויברכך, "The G–d of your father who helps you, and Shaddai who blesses you." The Zohar questions why the Torah wrote ואת שדי instead of וא-ל שדי. According to our approach the answer is simply that Jacob indicated that Joseph just like his father also has a part in the מצוה of תפילין, albeit in his capacity as an extension of his father. Therefore, Joseph's part in that מצוה is the phylacteries which are worn on the arm, and which feature the letters of the word שדי in the manner in which the strap is wound around the hand and the knot near the housing.