قَالَ أَمِيرُ الْمُؤْمِنِينَ ص لَا بَأْسَ بِالسَّلَمِ كَيْلًا مَعْلُوماً إِلَى أَجَلٍ مَعْلُومٍ لَا يُسْلَمُ إِلَى دِيَاسٍ وَ لَا إِلَى حَصَادٍ[2].
“Abu ‘ Abd Allah (a.s.), has said that ‘Amir al-Mu’minin has said, ‘Advance payment for a merchandise is not harmful if it is for known measures and appointed time. Advance payment is not made except for threshing and the time of harvest.’”