Hakeemul Ummat ra writes under the section of ‘Aqaid/Beliefs in Bashiti Zewar
General Beliefs #3.
By regarding a sin to be permissible, one’s Imaan (faith) goes away.
(Allah SWT protect us all from this. Ameen!)
General Belief s # 4.
No matter how serious a sin may be, as long as it is regarded as a sin, Imaan will remain. However, it (Imaan) does get weaker ([luster] diminishes).