As-Salam for a known specified weight Sahih al-Bukhari 2240b
Arabic hadith text
حَدَّثَنَا عَلِيٌّ، حَدَّثَنَا سُفْيَانُ، قَالَ حَدَّثَنِي ابْنُ أَبِي نَجِيحٍ، وَقَالَ، " فَلْيُسْلِفْ فِي كَيْلٍ مَعْلُومٍ إِلَى أَجَلٍ مَعْلُومٍ ".
Translation
Narrated Ibn Abi Najih
as above, saying, "He should pay the price in advance for a specified measure and for a specified period."