Buying a product on condition of not selling it
alsalamo alaikomhow are you Before asking you this long question let you know that i am a student prepaping for an academic exam, And there is an academic institution preparing people to study for this type of exams by giving books and video lectures at their centers,but you have to sign a paper states that after the end of the course you are not supposed to sell your books.the problem is that they charge a lot of money that i can't afford,so i went to one of the students in the course and i bought the books from him. My question is ,what is the rule of sharia'a in that, and if it is not permessible can i use the books in my study or not.thank you for your patience wa gazakom Allaho khaira