Narrated Abu Hurairah: "The Messenger of Allah (ﷺ) prohibited sales of Al-Munabadhah and Al-Mulamasah." He said: There are narrations on this topic from Abu Sa'eed and Ibn 'Umar. The Hadith is Abu Hurairah is a Hasan Sahih Hadith. And the meaning of (Munabadhah) in this Hadith is when it is said: "When I throw something to you then the sale between you and I is concluded." And Al-Mulamasah is that he says: "When you touch something then the sale is concluded." Even if he did not see it at all, like if it was inside of a bag or something else. There are merely sales practices of the people of Jahiliyyah so they were prohibited.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو كُرَيْبٍ، وَمَحْمُودُ بْنُ غَيْلاَنَ، قَالاَ حَدَّثَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ نَهَى رَسُولُ اللَّهِ صلى الله عليه وسلم عَنْ بَيْعِ الْمُنَابَذَةِ وَالْمُلاَمَسَةِ . قَالَ وَفِي الْبَابِ عَنْ أَبِي سَعِيدٍ وَابْنِ عُمَرَ . قَالَ أَبُو عِيسَى حَدِيثُ أَبِي هُرَيْرَةَ حَدِيثٌ حَسَنٌ صَحِيحٌ . وَمَعْنَى هَذَا الْحَدِيثِ أَنْ يَقُولَ إِذَا نَبَذْتُ إِلَيْكَ الشَّىْءَ فَقَدْ وَجَبَ الْبَيْعُ بَيْنِي وَبَيْنَكَ . وَالْمُلاَمَسَةُ أَنْ يَقُولَ إِذَا لَمَسْتَ الشَّىْءَ فَقَدْ وَجَبَ الْبَيْعُ وَإِنْ كَانَ لاَ يَرَى مِنْهُ شَيْئًا مِثْلَ مَا يَكُونُ فِي الْجِرَابِ أَوْ غَيْرِ ذَلِكَ وَإِنَّمَا كَانَ هَذَا مِنْ بُيُوعِ أَهْلِ الْجَاهِلِيَّةِ فَنَهَى عَنْ ذَلِكَ .
sunnah.com