Abu al-Hajjaj al-Azdi (may Allah have mercy on him) said: I heard Salman al-Farisi (may Allah be pleased with him) say in Isfahan: "A servant cannot be a believer until he knows that what has befallen him could not have missed him, and what has missed him could not have befallen him."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6035