Abu al-Bakhtari (may Allah have mercy on him) narrated: I asked Sayyiduna Ibn Abbas (may Allah be pleased with them both) about salam (advance payment sale) in date-palms, and he said: "The Messenger of Allah (peace and blessings be upon him) forbade selling (the produce of) date-palms until it can be eaten from, and until it is secured." I asked: What is meant by being secured? A man among those present said: "Until it is cut or stored."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12634