"The Messenger of Allah ﷺ forbade two kinds of transactions: Mulimasah and Mundbadhah.  

نَهَى رَسُولُ اللَّهِ ﷺ عَنْ بَيْعَتَيْنِ عَنِ الْمُلاَمَسَةِ وَالْمُنَابَذَةِ  

the Messenger of Allah ﷺ forbade Mulamasah and Munabadhah. (Sahih) Sahl added: "Sufyan said: 'Mulamasah means when a man touches something with his hand without seeing it, and Munabadhah means when he says: "Toss me what you have, and I will toss you what have."  

أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ الْمُلاَمَسَةِ وَالْمُنَابَذَةِ زَادَ سَهْلٌ قَالَ سُفْيَانُ الْمُلاَمَسَةُ أَنْ يَلْمِسَ الرَّجُلُ الشَّىْءَ بِيَدِهِ وَلاَ يَرَاهُ وَالْمُنَابَذَةُ أَنْ يَقُولَ أَلْقِ إِلَىَّ مَا مَعَكَ وَأُلْقِي إِلَيْكَ مَا مَعِي