Imam Ibnul Qaiyum said:
Temptations which are presented to the heart are a cause for its sickness, it is the temptations of desires and temptations of doubts…..
Imam Albani commented saying:
They [the temptations of desires and doubts] are the origin for every evil.
[Ighaathatul Lahfaan 1/42]
Majid Jawed Al Afghaanee