Mishkat al-Masabih 2936
Suhaib reported God's Messenger as saying, “There are three things which contain blessing:
A business transaction with a time specified, muqarada* and mixing wheat and barley for one’s household but not for sale.” 

Ibn Majah transmitted it.

* Giving someone some property to trade with, the profit being shared between the two, but any loss falling on the property.
عَن صُهَيْبٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: 
" ثَلَاثٌ فِيهِنَّ الْبَرَكَةُ: الْبَيْعُ إِلَى أَجَلٍ والمقارضة واخلاط الْبُرِّ بِالشَّعِيرِ لِلْبَيْتِ لَا لِلْبَيْعِ ". رَوَاهُ ابْنُ مَاجَه