Al-Muddaththir 74:18

According to the reports, al-Walid ibn al-Mughira, a wealthy and influential man of Quraysh, heard the Prophet recite the Quran and was deeply moved, openly acknowledging the beauty of its speech. Under pressure from his people, especially Abu Jahl, he pondered long, and finally declared: "This is nothing but magic handed down; this is nothing but the word of a mortal." Thereupon the verses were revealed, beginning "Leave Me alone with the one I created by himself," depicting his deliberation and his verdict.

Vâhidî, Esbâbü'n-Nüzûl; Hâkim, el-Müstedrek

Surah al-Muddaththir is Meccan and among the earliest revelations; according to the report from Jabir ibn Abdullah in Bukhari, its opening verses came down after the pause (fatra) that followed the first revelation. With the command 'Arise and warn' it inaugurated the mission of open proclamation. The later verses of the surah are reported to have been revealed concerning al-Walid ibn al-Mughira, a Meccan notable who called the Quran 'sorcery handed down'.

Buhârî rivayeti (Câbir hadisi); Vâhidî, Esbâbü'n-Nüzûl