Sahih Muslim 1519
Sahih Muslim · Book 21: The Book of Transactions · The prohibition of intercepting traders
Abu Huraira (Allah be pleased with him) reported Allah's Messenger (ﷺ) as saying:
حَدَّثَنَا ابْنُ أَبِي عُمَرَ ، حَدَّثَنَا هِشَامُ بْنُ سُلَيْمَانَ ، عَنِ ابْنِ جُرَيْجٍ ، أَخْبَرَنِي هِشَامٌ، الْقُرْدُوسِيُّ عَنِ ابْنِ سِيرِينَ ، قَالَ سَمِعْتُ أَبَا هُرَيْرَةَ ، يَقُولُ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " لاَ تَلَقَّوُا الْجَلَبَ . فَمَنْ تَلَقَّاهُ فَاشْتَرَى مِنْهُ فَإِذَا أَتَى سَيِّدُهُ السُّوقَ فَهُوَ بِالْخِيَارِ" .
Do not meet the merchant in the way and enter into business transaction with him, and whoever meets him and buys from him (and in case it is done, see) that when the owner of (merchandise) comes into the market (and finds that he has been paid less price) he has the option (to declare the transaction null and void).