In sefer Sichos HaChofetz Chaim the son of the Chofetz Chaim writes, that once the Chofetz Chaim was bentching and he got to the words, ואל תצריכנו לידי מתנת בשר ודם שלא נבוש ולא נכלם לעולם ועד – “We shouldn’t need to come onto receiving gifts from others, in order that we not be ashamed or humiliated for ever and ever”, and he let out a groan. After bentching his son asked him what the groan was about, and he answered as follows. The request of: שלא נבוש ולא נכלם לעולם ועד - “in order that we not be ashamed or humiliated for ever and ever” is difficult to understand, does a person live forever? Certainly not, so what are we asking for?
The Chofetz Chaim explained, sometimes a rich person supports a talmid chocham and helps him out as much as he can. The rich person is unable to learn, however, to ensure he gets reward in the Next World, he supports a talmid chocham and receives part of the talmud chocham’s reward. When this Zevulun comes to the Oilam HaEmes (the World of Truth, i.e. the Next World) and they ask him, “why didn’t you learn” he will answer that he supported a talmid chocham instead and agreed to split the reward. If, however, it turns out that the talmid chocham was a fraud and he never learnt lishma like he was supposed to, it will come out that not only will the talmid chocham not receive any reward, but his Zevulun will also not receive any reward. At that point the Zevulun will turn around to the talmid chocham and ask “why did you trick me? I didn’t learn because I was working hard to support you and was relying on you”. At that point the talmud chocham will be heavily ashamed, this type of shame is constant and applies even in the Oilam HaEmes. Therefore, in birchas hamazon we ask, ואל תצריכנו לידי מתנת בשר ודם - “please make us not need to come on to receiving help from others”, as we may not be able to learn Torah properly lishmah, and we will end up being humiliated in the world to come.
Besides for being a beautiful peshat in birchas hamazon, we see that the Chofetz Chaim agrees with the Maharash Primo, that if Yissachar learns lo lishmah, Zevulun loses out.
