Shaykhul-Islaam Ibn al-Qayyim (may Allah have mercy upon him) stated:

Allah The Most High stated: “The one who purified his soul is indeed successful and the one who corrupts his soul is indeed destroyed.” The meaning: The one who magnifies his soul, lifts it and makes it superior by way of being obedient to Allah is indeed successful. And the one who makes his soul inferior and insignificant and belittled it by way of disobedience to Allah is indeed the loser. There’s nothing that belittles the soul like disobedience to Allah. And there’s nothing that magnifies the soul, makes it honorable and raises it up (in status) like obedience to Him.

Source: (Al-Jawaab Al-Kaafi pg.52)

Translated by Abu Yusuf Khaleefah
12th of Rabee’ ath-Thaani, 1436 H (02-01-2015)
Masjid Nur Allah, Queens, NYC

Original Arabic

– قال ابن القيم – رحمه الله
قال الله تعالى: (قَدْ أَفْلَحَ مَنْ زَكَّاهَا وَقَدْ خَابَ مَنْ دَسَّاهَا). والمعنى: قد أفلح من كبَّرها وأعلاها بطاعة الله وأظهرها، وقد خسر من أخفاها وحقَّرها وصغَّرها بمعصية الله. فما صغَّر النفوس مثل معصية الله، وما كبَّرها وشرَّفها ورفَعَها مثل طاعته

(الجواب الكافي، ص: 52)