The Quran

وَقالَ الَّذينَ كَفَروا لِلَّذينَ آمَنوا لَو كانَ خَيرًا ما سَبَقونا إِلَيهِ ۚ وَإِذ لَم يَهتَدوا بِهِ فَسَيَقولونَ هٰذا إِفكٌ قَديمٌ

Muhammad Asad

But they who are bent on denying the truth speak thus of those who have attained to faith: "If this [message] were any good, these [people] would not have preceded us in accepting it!"¹ And sincethey refuse to be guided by it, they will always say, "This² is [but] an ancient falsehood!"

Lit., "towards it". Almost all of the classical commentators assume that this refers, specifically, to the contempt with which the pagan Quraysh looked down upon the early followers of Muhammad, most of whom came from the poorest, lowliest strata of Meccan society. However, the above "saying" has undoubtedly a timeless import inasmuch as the poor and lowly have always been among the first to follow a prophet. Moreover, it may also have a bearing on our times as well, inasmuch as the materially powerful nations, whom their technological progress has blinded to many spiritual verities, are increasingly contemptuous of the weakness of those civilizations in which religion still plays an important, albeit largely formalistic, role; and so, not realizing that this very formalism and the ensuing cultural sterility, and not religious faith as such, is the innermost cause of that weakness, they attribute it to the influence of religion per se, saying as it were, "If religion were any good, we would have been the first in holding on to it" - thus "justifying" their own materialistic attitude and their refusal to be guided by spiritual considerations.
I.e., the concept of divine revelation as such, as is evident from the subsequent reference to the revelation of Moses.