Maliks Muwatta Book 31, Hadith Number 76.
Yahya related to me from Malik from Muhammad ibn Yahya ibn Habban and from Abu’z-Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, forbade mulamasa and munabadha.
Malik said, “Mulamasa is when a man can feel a garment but is not allowed to unfold it or examine what is in it, or he buys by night and does not know what is in it. Munabadha is that a man throws his garment to another, and the other throws his garment without either of them making any inspection. Each of them says, ‘this is for this. ‘This is what is forbidden of mulamasa and munabadha.”
Malik said that selling bundles with a list of their contents was different from the sale of the cloak concealed in a bag or the cloth folded up and such things. What made it different was that it was a common practice and it was what people were familiar with, and what people had done in the past, and it was still among the permitted transactions and trading of people in which they saw no harm because in the sale of bundles with a list of contents without undoing them, an uncertain transaction was not intended and it did not resemble mulamasa.