Sforno on Genesis 49:22/ספורנו על בראשית מ״ט:כ״ב

1בן פורת יוסף, Joseph is considered the product of a proliferating grapevine. It spreads its protective shade for the benefit of many. In Psalms 80,11 we are told of this function of the grapevine in the words כסו הרים צלה, “the mountains were covered by its shade.” The simile means that Yaakov and his family lived under the protective cover of Joseph, i.e. in his shade.

2The word פורת derivative of פוריה, fruitful, implies the proximity of a spring, a well of water. בנות, branches. The grapevine brings forth many branches.

3צעדה עלי שור, describing how these branches even grow beyond the wall surrounding the orchard. Alternatively, what is meant is that the branches extend beyond the fence surrounding the well. Prior to its prolific growth it could not be seen from the far side of the wall. People living on that side of the wall did not even have an idea that something was growing there. Once the branches had topped the wall, its presence suddenly became noticeable and provoked reactions on the other side. The other side of the parable, are, of course, Yaakov on the one hand, and Joseph and his sons, who had developed in Egypt without their father even being aware that they were alive. Suddenly, what had been hidden from him for 22 years had become revealed. This is what he meant when he said on meeting him: ראה פניך לא פללתי והנה הראה אותי אלוקים גם את זרעך, I did not even expect ever to see your face again, and now G’d has shown me not only you but also your offspring. (48,11)