ما هي الآيات القرآنية أو الأحاديث النبوية أو قصص الصحابة التي تحث على إخفاء أمور التجارة والعقود عن غير المعنيين بها؟

A person should keep their private matters and secrets confidential, because the Prophet (ﷺ) said: "Seek help for the achievement of your needs by being discreet, for every person of blessing is envied." So, the person who has a blessing is envied, and keeping the matter confidential wards off envy, especially if the matter has not yet been completed. By doing so, one protects themselves from the competition of rivals and the envy of the envious. It is also recommended for him to strive in supplications to repel the evil of the envious and to recite the two refuge-seeking surahs (al-Mu'awwidhatayn) upon himself as a ruqyah.