How one looses his Deen by loosing Adab:
When one begins to compromise on the minor Deeni practices (if they could be referred to as minor) then there is no stopping. It’s like slippery ice, and slippery ice no joke!
The following has been reported from the Salaf (pious predecessors) among them, Imams Ruwaim (rahimahullah) and Abu ‘Ali Ad-Daqqaq (rahimahullah):
من تهاون بالآداب عوقب بحرمان السنة ومن تهاون بالسنة عوقب بحرمان الفرائض، ومن ترك الفرائض عوقب بحرمان المعرفة
“Whoever belittles Adab (etiquette) will be punished by being deprived of the sunnah, and who leaves a sunnah will be deprived of the fardh (obligatory) deeds and he will eventually be deprived of his recognition of Allah (Imaan)”
-(Kitabut- Tahajjud of Ishbili, pg.132 & Mu’eedun Ni’am of Subki, pg. 85)
(Taken from almiftah blog of Maulana Muhammad)