Indeed, those who lower their voices before the Messenger of Allāh - they are the ones whose hearts Allāh has tested for righteousness. For them is forgiveness and great reward.
In the Name of Allah, the Most Gracious, the Most Merciful.
The Prohibition of making a Decision in advance of Allah and His Messenger; ordering Respect towards the Prophet
In these Ayat, Allah the Exalted teaches His faithful servants the good manners they should observe with the Messenger ﷺ, which are respect, honor and esteem. Allah the Exalted and Most Honored said,
(O you who believe! Make not (a decision) in advance before Allah and His Messenger,) meaning, do not rush in making decisions before him, rather, follow his lead in all matters. `Ali bin Abi Talhah reported that Ibn `Abbas, may Allah be pleased with him, commented;
لَا تَرْفَعُوا أَصْوَاتَكُمْ فَوْقَ صَوْتِ النَّبِيِّ do not raise your voices above the voice of the Prophet ﷺ . - 49:2) This is another etiquette to be observed while in the presence of the Holy Prophet ﷺ . This verse teaches the believers that they should not raise their voices above the voice of the Holy Prophet ﷺ nor speak aloud to him as one speaks aloud to another in general discussions. The verse warns that neglecting this etiquette may entail nullification of one's virtuous deeds, because this is a kind of disrespect to the Holy Prophet ﷺ . Thus when this verse was revealed, the blessed Companions ؓ became very apprehensive and very cautious. Sayyidna Abu Bakr ؓ said: "By God! 0 Messenger of Allah, from now till my last breath, I shall speak to you as if someone is whispering." (Ad-Durr-ul Manthur on the authority of Baihaqi) When this verse was revealed, Sayyidna ` Umar's ؓ voice became so low that the Holy Prophet ﷺ had to ask him to repeat what he said, so that he could understand what he was saying to him (Sihah). Thabit Ibn Qays ؓ had a naturally loud voice. When he heard this verse, he feared that his good deeds would be rendered void, he wept and lowered his voice (Ad-Durr-ul-Manthur on the authority of Baihaqi).
To hold one’s opinion superior to that of the Prophet is forbidden. During the life of the Prophet Muhammad, this attitude on the part of an addressee took the shape of indulgence in verbosity at his meetings, the object being to excel the Prophet’s discourse. Subsequently, this meant the forming of opinions in disregard of the guiding principles laid down by God and His Prophet. This sort of lapse occurs because man forgets that God is keeping a watch over him. If he came to know that his utterances reached God before they reached other human beings, he would prefer to remain silent rather than talk.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.