Allah Almighty said:
اتَّبِعُوا مَا أُنْزِلَ إِلَيْكُمْ مِنْ رَبِّكُمْ وَلَا تَتَّبِعُوا مِنْ دُونِهِ أَوْلِيَاء
Reference: (Surah Al-A'raf: 3)
Translation: "Follow what has been revealed to you from your Lord, and do not follow other protectors besides Him."
And He said:
فَبِأَيِّ حَدِيثٍ بَعْدَهُ يُؤْمِنُونَ
Reference: (Surah Al-A'raf: 185)
Translation: "Then after this, of what are they going to believe?"
From these two verses, it is understood that servants are not obligated to follow anything other than the Holy Quran!
In the first verse, Allah, the Lord of the Worlds, commands the believers to remain steadfast on the revelation and forbids following false paths, as scholars have mentioned in the exegesis of this verse.
Imam Al-Qurtubi, may Allah have mercy on him, says:
The blessed verse
اتَّبِعُوا مَا أُنْزِلَ إِلَيْكُمْ مِنْ رَبِّكُمْ
Translation: "Follow what has been revealed to you from your Lord."
This means the Book and the Sunnah... that is, follow the religion of Islam and the Quran, consider what has been made lawful as lawful and what has been made unlawful as unlawful, comply with its commands, and avoid its prohibitions.
Reference: (Al-Jami' li Ahkam al-Qur'an: 7/161)
First Point
Is it conceivable that Allah Almighty sends a Messenger and reveals revelation to him and commands obedience to that Messenger, as He said:
مَنْ يُطِعِ الرَّسُولَ فَقَدْ أَطَاعَ اللَّهَ وَمَنْ تَوَلَّى فَمَا أَرْسَلْنَاكَ عَلَيْهِمْ حَفِيظًا
Reference: (Surah An-Nisa:80)
Translation: Whoever obeys the Messenger has indeed obeyed Allah, and whoever turns away - We have not sent you over them as a guardian.
وَمَا آتَاكُمُ الرَّسُولُ فَخُذُوهُ وَمَا نَهَاكُمْ عَنْهُ فَانْتَهُوا
Reference: (Surah Al-Hashr:7)
Translation: And whatever the Messenger gives you, take it, and whatever he forbids you, refrain from it.
And then the same Messenger is set against oneself and one is warned against following him?! This is completely contrary to justice and wisdom, which is impossible for Allah, the Lord of the Worlds.
Second Point
From the background of the second verse, it is clear that this verse is about those people who chose disbelief over Islam and denied the signs of Allah.
Allah Almighty says:
وَالَّذِينَ كَذَّبُوا بِآيَاتِنَا سَنَسْتَدْرِجُهُمْ مِنْ حَيْثُ لَا يَعْلَمُونَ وَأُمْلِي لَهُمْ إِنَّ كَيْدِي مَتِينٌ أَوَلَمْ يَتَفَكَّرُوا مَا بِصَاحِبِهِمْ مِنْ جِنَّةٍ إِنْ هُوَ إِلَّا نَذِيرٌ مُبِينٌ أَوَلَمْ يَنْظُرُوا فِي مَلَكُوتِ السَّمَاوَاتِ وَالْأَرْضِ وَمَا خَلَقَ اللَّهُ مِنْ شَيْءٍ وَأَنْ عَسَى أَنْ يَكُونَ قَدِ اقْتَرَبَ أَجَلُهُمْ فَبِأَيِّ حَدِيثٍ بَعْدَهُ يُؤْمِنُونَ
Reference: (Surah Al-A'raf:182-185)
Translation: And those who deny Our verses, We will surely gradually lead them away where they do not know. And I will grant them respite; indeed, My plan is firm. And have they not considered what madness is in their companions? He is nothing but a clear warner. And have they not looked at the dominion of the heavens and the earth and anything that Allah has created, and that perhaps their appointed time is indeed near? Then what will they believe in after that?
Third Point
The above two verses are from Surah Al-A'raf, which is a Makki Surah, and among the themes and characteristics of Makki Surahs is the topic of inviting the deniers of the Quran to confirm the Quran and act upon it, which is as clear as daylight from the interpretation of the verses.
Therefore, understanding these verses as a prohibition on following the Sunnah is in no way correct.
Fourth Point
In the mentioned Surah Al-A'raf, Allah Almighty says:
الَّذِينَ يَتَّبِعُونَ الرَّسُولَ النَّبِيَّ الْأُمِّيَّ الَّذِي يَجِدُونَهُ مَكْتُوبًا عِنْدَهُمْ فِي التَّوْرَاةِ وَالْإِنْجِيلِ يَأْمُرُهُمْ بِالْمَعْرُوفِ وَيَنْهَاهُمْ عَنِ الْمُنْكَرِ وَيُحِلُّ لَهُمُ الطَّيِّبَاتِ وَيُحَرِّمُ عَلَيْهِمُ الْخَبَائِثَ وَيَضَعُ عَنْهُمْ إِصْرَهُمْ وَالْأَغْلَالَ الَّتِي كَانَتْ عَلَيْهِمْ فَالَّذِينَ آمَنُوا بِهِ وَعَزَّرُوهُ وَنَصَرُوهُ وَاتَّبَعُوا النُّورَ الَّذِي أُنْزِلَ مَعَهُ أُولَئِكَ هُمُ الْمُفْلِحُونَ
Reference: (Surah Al-A'raf:157)
Translation: Those who follow the Messenger, the unlettered prophet, whom they find written in the Torah and the Gospel, who enjoins upon them what is right and forbids them what is wrong, and makes lawful for them the good things and prohibits for them the impure, and relieves them of their burden and the shackles which were upon them. So those who believe in him, honor him, help him, and follow the light which has been sent down with him - it is they who will be successful.
So how is it possible that on one hand Allah, the Lord of Glory, praises these noble companions and declares them successful and prosperous, highlighting their special characteristic that they follow the Noble Prophet ﷺ, and then on the other hand, condemns this praiseworthy act of theirs!