عن عبد الله بن مسعود رضي الله عنه قال: إني لأحسب الرجل ينسى العلم كما تعلمه للخطيئة يعملها (الترغيب والترهيب، الرقم: 224)

It is reported that Hazrat Abdullah bin Mas’ood (radhiyallahu ‘anhu) once mentioned, “I certainly know that on account of the sin that a person commits, he forgets the knowledge of deen as he had learnt it.”

Note: When a person commits sins, then due to the ill-effects of the sin, a person is deprived of the noor and barakah of ilm. At times, he is deprived of the true understanding of the knowledge, and at times, he forgets the knowledge entirely – may Allah Ta‘ala save us!