Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: "Ukaz, Majannah and Dhu al-Majaz were markets in the Days of Ignorance (Jahiliyyah). When Islam came, the people considered it sinful to trade during Hajj, so Allah, the Mighty and Majestic, revealed this verse: 'There is no sin upon you in seeking bounty from your Lord' [Al-Baqarah: 198]" - that is, during the seasons (days) of Hajj.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11167