Is it obligatory to inform the buyer about a defect in a commodity if he does not ask about it?

The seller must disclose defects in the merchandise that diminish its value and desirability, based on religious evidences, including: "A Muslim is the brother of a Muslim. It is not permissible for a Muslim who sells to his brother a sale that contains a defect, except that he discloses it to him," and the hadith: "Whoever cheats us is not of us."