Two types of trarisactions have been forbidden (by the Holy Prophet), al-Mlulamasa and al-Munabadha. As far as Mulamasa transaction is concerned, it is that every one of them (the parties entering into transaction) should touch the garment of the other without careful consideration, and al-Munabadha is that every one of them should throw his cloth to the other and one of them should not see the cloth of his friend.
عَنْ بَيْعَتَيْنِ الْمُلاَمَسَةِ وَالْمُنَابَذَةِ أَمَّا الْمُلاَمَسَةُ فَأَنْ يَلْمِسَ كُلُّ وَاحِدٍ مِنْهُمَا ثَوْبَ صَاحِبِهِ بِغَيْرِ تَأَمُّلٍ وَالْمُنَابَذَةُ أَنْ يَنْبِذَ كُلُّ وَاحِدٍ مِنْهُمَا ثَوْبَهُ إِلَى الآخَرِ وَلَمْ يَنْظُرْ وَاحِدٌ مِنْهُمَا إِلَى ثَوْبِ صَاحِبِهِ