But they know not

And when it is said to them, "Believe as the people have believed," they say, "Should we believe as the fools have believed?" Unquestionably, it is they who are the foolish, but they know [it] not.

[Qur'ān 2:13]

Imām al-Qurtubi writes that a group of scholars are of the view that the Verse refers to the munāfiqūn. Another group of scholars believes it refers to the Jews when they were told to believe as Abd bin Salām and his companions had done so to which they replied should we believe like the fools have done so.

Ibn Kathīr writes in his Tafsīr that the portion of the Verse which reads "but they do not know," means that it is a part of the completeness of their ignorance that they do not know of their state of how misguided and ignorant they are.