The ruling on a partner selling his goods from his own wealth to a mudarabah partnership

Question:
Also, a person says: Two people entered into a mudarabah (profit-sharing partnership), and one of them bought a commodity from his own wealth and then sold it to the partnership, knowing that his partner did not know that the commodity belonged to him. What is the ruling on that?

Answer:
This is not permissible, because the partner is an agent for his partner, and an agent does not sell to himself, nor does he put any of his own wealth into the partnership. Therefore, such a transaction is not valid, because it is a betrayal of the partner.