"A person who reports disbelief is not a disbeliever." What is the origin of this statement and who said it? Is this considered a Figh rule? [Please clarify in details].

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The rule: ''A person who reports disbelief is not a disbeliever'' is an expression that is mentioned by some scholars like Ibn Katheer and Shayt Ibn Haydarah. This rule is correct if the person who reports disbelief is only narrating it, or that he is narrating it and responding to it. There is much of this in the Quran and in the Sunnah of the Prophet . However, if the person who reports disbelief, reports it while believing in it and agreeing with it, then he is a disbeliever like the one who said it.

Nonetheless, this is not one of the Fiqh rules; rather it is one of the rules in creed in the field of Takfeer [declaring someone a disbeliever]. 

Allaah Knows best.