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)
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 44
Arabic reference: Book 65, Hadith 4519