Is it permissible to purchase books that some professors sell to the general public and students, knowing that they obtained them for free or at a very low price from publishing platforms designated for professors and doctors, and that selling them violates the terms of the publishing company, which has warned against their sale and against their reaching students?

It is not permissible for doctors to violate the conditions for downloading and utilizing books, due to the Prophet's (peace be upon him) saying: «Muslims are bound by their conditions.» Nor is it permissible to purchase these books from those known not to have permission to sell them, because it constitutes cooperation in sin, which is forbidden, as Allah Almighty says: {And do not cooperate in sin and aggression.}