Sri M said....

There is a small word in between ‘Upa’ and ‘shad’ - ‘Ni’. ‘Ni’ indicates the position of one who teaches and one who's listening. The student sits with the attitude, ‘I don’t know, let me understand.’ It means listening as if one is hearing it for the first time. ‘Ni’ also means the receiving vessel is placed lower than the source of knowledge. And, it has to be empty. Space is required to imbibe knowledge.