Do not raise your voice above his

O you who have believed, do not raise your voices above the voice of the Prophet or be loud to him in speech like the loudness of some of you to others, lest your deeds become worthless while you perceive not.

[Qur'aan 49:2]

Allaah has forbidden you to raise your voice in his (sallallaahu alayhi wa sallam) presence lest he (sallallaahu alayhi wa sallam) becomes angry because of that and as a result of that Allaah becomes angry because of his (sallallaahu alayhi wa sallam) anger and renders the deeds of the one He is angry with futile while he does not know as has come in the authentic hadith:

Abu Hurairah (May Allah be pleased with him) reported:

The Prophet (sallallaahu alayhi wa sallam) said, "A man utters a word pleasing to Allah without considering it of any significance for which Allah exalts his ranks (in Jannah); another one speaks a word displeasing to Allah without considering it of any importance, and for this reason he will sink down into Hell."

[Sahih al-Bukhaari Hadith No. 1515]

Reference(s):

Tafsir Ibn Kathiir