It is narrated about Sayyiduna Jarir al-Bajali (may Allah be pleased with him) that whenever he offered goods for sale, he would point out their defects, then give the buyer the choice and say: If you wish, take it, and if you wish, leave it. It was said to him: May Allah have mercy on you, if you do this, your sales will not go through. He said: "We pledged allegiance to the Messenger of Allah (peace and blessings be upon him) on sincere goodwill towards the people of Islam."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2497