Mu’âwiyah b. Qurrah reports that Abû Al-Dardâ` used to say,
Nas alullaaha eemaanan daayiman, wa yaqeenan saadhiqan, wa ilman naafiyan
Mu’âwiyah b. Qurrah then said,
“So this indicates that there is a type of faith that does not last, and a type of certainty that is not true, and a type of knowledge that is not beneficial.”
Ibn Battah, Al-Ibânah Al-Kubrâ Vol. 2 p498.
Source : http://www.sayingsofthesalaf.net