﴿ وَمَا هُوَ بِقَوْلِ شَاعِرٍۢ ۚ قَلِيلًۭا مَّا تُؤْمِنُونَ ﴾

“and is not – however little you may [be prepared to] believe it - the word of a poet;”

(It) i.e. the Qur'an (is not poet's speech) that a poet composes (little is it that ye believe!) He says: you do not believe in little or much.