Sunan Ibn Majah
2214
Sahih+3

It was narrated from Ibn 'Umar that the Messenger of Allah (ﷺ) said:"Do not sell fruits until they have ripened." And he forbade (both) the seller and the purchaser (to engage in such a transaction)

SahihAl-Albani
SahihMuhammad Fouad Abd al-Baqi