Honest trade is blessed
الْبَيِّعَانِ بِالْخِيَارِ مَا لَمْ يَتَفَرَّقَا، فَإِنْ صَدَقَا وَبَيَّنَا بُورِكَ لَهُمَا فِي بَيْعِهِمَا، وَإِنْ كَذَبَا وَكَتَمَا مُحِقَتْ بَرَكَةُ بَيْعِهِمَا
Al-bayyi'ani bi-l-khiyari ma lam yatafarraqa, fa-in sadaqa wa bayyana burika lahuma fi bay'ihima, wa in kadhaba wa katama muhiqat barakatu bay'ihima.
"The buyer and the seller may cancel the sale as long as they have not parted. If they speak the truth and make everything clear, their sale is blessed for them. If they lie and hide things, the blessing of their sale is wiped out."
Narrated by Hakim ibn Hizam. Sahih Muslim 1532, Sahih al-Bukhari 2079
A short reflection
Barakah in business is tied to two things you control: telling the truth and showing the flaw. Profit made by hiding it costs more than it earns.