Assalāmu ‛Alaykum Wa Rahmatullāhi Wa Barakātuhu.
Ibn Qayyim رحمه الله said:
“Sins have many side effects. One of them is that they steal knowledge from you.” [Ad da, Page:65]
Al-Hasan Al-Basree رحمه الله said:
“Verily, a man commits a sin and never forgets it and he won’t cease to be afraid of it until he enters Paradise.” [Az-Zuhd of Imaam Ahmad, Page: 338]
Ibn al-Qayyim رحمه لله said:
No slave of Allah commits a sin except that a blessing from Allah is removed from him equal to that sin. [Tareeq, Volume: 1, Page: 271]
Sufyaan Ibn ‘Uyaynah (d.198H) رحمه الله said:
“He whose sin is due to desire, then have hope for him; and he whose sin is due to pride, then fear for him. Because Adam (alayhis-salaam) sinned due to desire, and he was forgiven; and Iblis sinned due to pride, and he was cursed.” [Related by Imaam adh-Dhahabee in Siyar A’laamun-Nubalaa (8/471)]
Ibn al-Qayyim: Some of the Salaf said:
“I committed one sin and due to it, I was prevented from Qiyaam al-Layl one year” [Tareeq, Page: 408]
Ibn Mas’ood رضي الله عنه said:
“Indeed, I consider that the man forgets the knowledge which he knew he has because of the sin he commits” [Az-Zuhd 1/129]
Ibn al-Qayyim رحمه الله said:
“If you sin it will create a defect in you that may never be removed.” [al-Fawaa-id, Page: 340]
Ibn al-Qayyim رحمه الله said:
“Enough as a punishment for sins is that it prevents you from worshiping Allah, even if you wanted to.” [ad-Daa’, Page: 87]
Imaam Ibn ul-Qayyim رحمه الله said:
“Sins are wounds and one wound may cause death.” [al-Fawā’id, Page: 65]
Ibn Al Qayyim رحمه الله said:
“Man almost forgets the knowledge he has gained because of the sins he has committed.” [Al-Fawā’id Page: 248]
Ibn Taymiyyaah رحمه الله said:
“Sins cause harm & repentance removes the cause.” [Majmoo-ul-Fataawaa, 10/255]
The Salaf used to say:
“Sins lead to kufr, kisses to intercourse, songs to Zina, a sight to falling in love, and a disease to death.” [Ad-Da’, Page: 62]
