‘Awf reported: I entered the home of Ibn Sirin, may Allah have mercy on him, and I began discussing the sins of the ruler Al-Hajjaj. Ibn Sirin said, “Verily, Allah Almighty is a just judge. Just as he passes judgment against Al-Hajjaj, he will pass judgment in favor of Al-Hajjaj. If you were to meet Allah tomorrow, the smallest sin you committed would be worse for you than the greatest sin Al-Hajjaj committed against you.”
Al-Qushayri said, “It is said that a servant will receive his book of deeds on the Day of Resurrection and he will not see any good in it. He will say: Where are my prayers? Where is my fasting? Where are my acts of obedience? It will be said: All of your good deeds have been lost because you were backbiting against people.”
Source: al-Risālah al-Qushayrīyah 1/291
عن عوف دخلت عَلَى ابْن سيرين رحمه الله فتناولت الْحَجَّاج فَقَالَ ابْن سيرين إِن اللَّه تَعَالَى حكم عدل فكما يأخذ من الْحَجَّاج يأخذ للحجاج وإنك إِذَا لقيت اللَّه عَزَّ وَجَلَّ غدا كَانَ أصغر ذنب أصبته أشد عليك من أَعْظَم ذنب أصابه الْحَجَّاج
وقال القشيرية قيل يؤتى العبد يَوْم الْقِيَامَة كتابه فلا يرى فِيهِ حسنة فَيَقُول أين صلاتي وصيامي وطاعاتي فيقال ذهب عملك كُلهُ باغتيابك لِلنَّاسِ
1/291 الرسالة القشيرية