Abu al-Bakhtari says: I asked Abdullah bin Umar (may Allah be pleased with them both) about the salam sale made in dates, and he said: "The sale of dates has been forbidden until they ripen." He says: Then I asked Abdullah bin Abbas (may Allah be pleased with them both), and he said: "The sale of dates has been forbidden until they can be eaten from and can be weighed."
Imam Shu'bah (may Allah have mercy on him) says: I asked a man sitting beside (him): "What is meant by being weighed?" He said: "That it has been picked and secured."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11110
Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that Sayyiduna Umar (may Allah be pleased with him) forbade "selling fruit before it ripens" and forbade "selling silver for gold on credit." And in the explanation it is stated: I said: "What is meant by weighing?" A man sitting with him said: "That it can be secured."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11111
A man from the people of Najran asked Sayyiduna Ibn Umar (may Allah be pleased with them both) about making a salam sale in dates. He said: A man made a salam sale in dates with another man, and that year the palms bore no fruit. He put the matter before the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Why do you consume his wealth?" He (peace and blessings be upon him) ordered him to return (the price) to him for the sale. Then he (peace and blessings be upon him) forbade making a salam sale in dates until the fruit ripens.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11112
Sayyiduna Ibn Umar (may Allah be pleased with them both) says: A man made a salaf sale in dates with another man, and that year the palms bore no fruit. They brought the dispute to the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Why do you consider his wealth lawful for yourself? Return it to him." Then he (peace and blessings be upon him) said: "Do not make salaf sales in dates before they ripen."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11113
Sayyiduna Abdullah bin Salam (may Allah be pleased with him) says: When Allah Almighty willed to guide Zayd bin Sa'nah (may Allah be pleased with him), then he narrated the whole hadith, until he said: Zayd bin Sa'nah said to him (peace and blessings be upon him): "O Muhammad! Will you sell me dates whose term is known, whose weight is known, and the garden from which they are to be given is also known?" He (peace and blessings be upon him) said: "O Jew! I will sell you dates; the weight will be known and the term too, but there will be no condition as to which garden they are to be given from." He says: I said: "Very well." Then I opened my purse and gave eighty dinars.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 11114