عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ رَضِيَ اللَّهُ عَنْهُ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ نَهَى عَنِ اسْتِئْجَارِ الْأَجِيرِ حَتَّى يُبَيَّنَ أَجْرَهُ وَعَنِ النَّجْشِ وَاللَّمْسِ وَإِلْقَاءِ الْحَجَرِ
It is narrated from Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) forbade employing a laborer without fixing his wages, forbidden najsh sale, forbidden mulamasah sale, and forbidden trading by throwing a stone.