Al-Matalib al-'Aliyah 2878 — Defining Islam and faith

It is narrated from Ubayd bin Umar (may Allah have mercy on him), (the narrator said): I heard him saying: "Faith (in its state) is like gusts and waves of wind (which are sometimes strong and sometimes faint)."
Imam Musaddad (may Allah have mercy on him) recorded this report in his Musnad.