Ibn al-Qayyim (rahimahullaah) said:
“Eemaan is a reason for bringing about every good, and every good in the life of this world and the Hereafter – its factor is Eemaan. Likewise every evil in the life of this world and the Hereafter – its reason is an absence of Eemaan..”
Selected from: https://www.wrightstreetmosque.com/complacency-in-committing-sins-and-persisting-upon-them-its-dangers-and-addressing-some-common-excuses-related-to-sinning/
Translated by Abu Haatim M. Farooq
