Imām Ibn al-Qayyim (d. 751 AH) said:

Most people lack knowledge concerning the sins that destroy their deeds of goodness. Indeed, the Most High said:

يَا أَيُّهَا الَّذِينَ آمَنُوا لَا تَرْفَعُوا أَصْوَاتَكُمْ فَوْقَ صَوْتِ النَّبِيِّ وَلَا تَجْهَرُوا لَهُ بِالْقَوْلِ كَجَهْرِ بَعْضِكُمْ لِبَعْضٍ أَن تَحْبَطَ أَعْمَالُكُمْ وَأَنتُمْ لَا تَشْعُرُونَ

“O you who believe! Raise not your voices above the voice of the Prophet (صلى الله عليه وسلم), nor speak aloud to him in talk as you speak aloud to one another, lest your deeds may be rendered fruitless while you perceive not. “
(Ḥujurāt, 49:2)

The Most Exalted has warned the believers of the destruction of their good deeds and it being rendered fruitless as a result of speaking aloud to the Messenger of Allāh (صلى الله عليه وسلم) in a manner similar to the way the people speak to one another. Doing so is not a form of apostation, rather a grave sin that destroys deeds of piety while the person does not perceive it.

What, then, should we surmise regarding those who put forward the opinion, perceived guidance, and way of men, over the saying of the Messenger (صلى الله عليه وسلم), his guidance, and way?! Is such a person not also deserving of having his actions destroyed without him even perceiving it?!

Source: al-Wābil al-Ṣayyib: 21
Translated by: Riyāḍ al-Kanadī