‏البر والصلة والآداب‏ : Hadeeth No:6241 'A'isha reported: I heard Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: There is nothing (in the form of trouble) that comes to a believer even if it is the pricking of a thorn that there is decreed for him by Allaah good or his sins are obliterated....

‏الحج : Hadeeth No:3190 This hadith has been narrated by Yabya b. Sa'id with the same chain of transmitters (and the words are):" Just as a furance removes impurity," but no mention is made of iron....