The Messenger of Allah ﷺ forbade selling grapes until they darken and forbade selling grain until it hardens.
حدثنا الحسن بن علي الخلال حدثنا أبو الوليد وعفان وسليمان بن حرب قالوا حدثنا حماد بن سلمة عن حميد
أن رسول الله ﷺ نهى عن بيع العنب حتى يسود وعن بيع الحب حتى يشتد
[Its chain of transmission is daif]. Abu Dawud reported it in the Book of Sales, chapter on selling fruits before their soundness becomes apparent, no. 3371, from Hasan bin Ali, and Ibn Majah, no. 2217, narrated it from the hadith of Hammad bin Salama with the same wording. Humayd narrated it using "an" without specifying direct transmission. Ibn Hibban graded it sahih (al-Ihsan, 4972), as did Hakim, 2/19, saying it meets the standard of the two Shaykhs (Bukhari and Muslim), and Dhahabi agreed with him.