Sahih al-Bukhari 4519
Narrated Ibn `Abbas:
`Ukaz, Mijanna and Dhul-Majaz were markets during the Pre-islamic Period. They (i.e. Muslims) 
considered it a sin to trade there during the Hajj time (i.e. season), so this Verse was revealed:-- 
"There is no harm for you if you seek of the Bounty of your Lord during the Hajj season." (2.198)
حَدَّثَنِي مُحَمَّدٌ، قَالَ أَخْبَرَنِي ابْنُ عُيَيْنَةَ، عَنْ عَمْرٍو، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ كَانَتْ عُكَاظٌ وَمَجَنَّةُ وَذُو الْمَجَازِ أَسْوَاقًا فِي الْجَاهِلِيَّةِ فَتَأَثَّمُوا أَنْ يَتَّجِرُوا فِي الْمَوَاسِمِ فَنَزَلَتْ ‏{‏لَيْسَ عَلَيْكُمْ جُنَاحٌ أَنْ تَبْتَغُوا فَضْلاً مِنْ رَبِّكُمْ‏}‏ فِي مَوَاسِمِ الْحَجِّ‏.‏