Sighting or calculation

Our Deen Islam is based on one thing only and that is trust in the truthfulness of our Prophet Muhammadﷺ. We believe that the Ayaat of the Qur’an are the speech of Allahﷻ because Muhammadﷺ said so. That is why we treat the Ahadith of Rasoolullahﷺ with so much reverence because they were also said by the same person, i.e., Muhammadﷺ, who recited for us, the Word of Allahﷻ. It is a measure and proof of his truthfulness that he never claimed his speech to be the Word of God – Kalaamullah, even though Allahﷻ said about the speech of Muhammadﷺ:

وَمَا يَنطِقُ عَنِ ٱلْهَوَىٰٓ - إِنْ هُوَ إِلَّا وَحْىٌ يُوحَىٰ

Najm 53: 3-4   Nor does he speak of his own volition. It is only a revelation sent ˹to him˺.

Allahﷻ commanded us, Believers, to obey Muhammadﷺ unquestioningly.

وَمَآ ءَاتَىٰكُمُ ٱلرَّسُولُ فَخُذُوهُ وَمَا نَهَىٰكُمْ عَنْهُ فَٱنتَهُوا۟ وَٱتَّقُوا۟ ٱللَّهَ إِنَّ ٱللَّهَ شَدِيدُ ٱلْعِقَابِ

Hashr 59: 7    Whatever the Messenger gives you, take it. And whatever he forbids you from, leave it. And fear Allah. Surely Allah is severe in punishment.

Allahﷻ didn’t restrict obedience to Rasoolullahﷺ to worship alone or anything else. He gave a blanket command and ordered us to obey Rasoolullahﷺ in every matter and warned us of His punishment if we didn’t obey Rasoolullahﷺ without question.  Let us remember that Islam means submission and it is only obedience which makes us Muslims.

Finally, for the purpose of our discussion here, Allahﷻ declared on oath by Himself that we can’t have faith until we accept the rulings of Rasoolullahﷺ in all matters wholeheartedly without any resistance to them in our hearts.

فَلَا وَرَبِّكَ لَا يُؤْمِنُونَ حَتَّىٰ يُحَكِّمُوكَ فِيمَا شَجَرَ بَيْنَهُمْ ثُمَّ لَا يَجِدُوا۟ فِىٓ أَنفُسِهِمْ حَرَجًا مِّمَّا قَضَيْتَ وَيُسَلِّمُوا۟ تَسْلِيمًا

Nisa 4: 65    But no! By your Rabb, they will never be believers until they accept you ˹O Prophet˺ as the judge in their disputes and find no resistance within themselves against your decision and submit wholeheartedly.

Based on this our scholars from the Sahaba onwards have always taken the position that anyone who denies a Sahih Hadith or refuses to accept a ruling of Rasoolullahﷺ, has committed Kufr and has left Islam.

https://islamqa.info/en/answers/115125/ruling-on-one-who-rejects-a-saheeh-hadith

That is the light in which we must see the following Hadith of Rasoolullahﷺ:

عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مَنْ رَغِبَ عَنْ سُنَّتِي فَلَيْسَ مِنِّي

Abdullah ibn Amr (RA) reported: Rasoolullahﷺ  said, “Whoever does not desire my Sunnah is not a part of me.” (Sunan Ibn-Abi Asim) Hadith Sahih (Al-Albani)

For those who love His Messengerﷺ and emulate him, Allahﷻ promised:

قُلْ إِن كُنتُمْ تُحِبُّونَ ٱللَّهَ فَٱتَّبِعُونِى يُحْبِبْكُمُ ٱللَّهُ وَيَغْفِرْ لَكُمْ ذُنُوبَكُمْ وَٱللَّهُ غَفُورٌ رَّحِيمٌ

A’al Imraan 3: 31   Say, ˹O Prophet,˺ “If you ˹sincerely˺ love Allah, then emulate me; Allah will love you and forgive your sins. For Allah is All-Forgiving, Most Merciful.”

Finally, Allahﷻ said about this Deen of ours Islam:

ٱلْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِى وَرَضِيتُ لَكُمُ ٱلْإِسْلَـٰمَ دِينًا

Ma’ida 5: 3    Today I have perfected your faith for you, completed My favor upon you, and chosen Islam as your way.

About when this Ayah was revealed, we have the narration where a Jew said to 'Umar ibn Al Khattab (R), 'O leader of the believers! There is an Ayah in your Book (Qur’an) which is read by all of you (Muslims), and had it been revealed to us (Jews), we would have taken that day (on which it was revealed) as a day of celebration." 'Umar Ibn Al Khattab (R) asked him, "Which Ayah is that?" The man replied: "This day I have perfected your religion for you, completed My Favor upon you, and have chosen for you Islam as your religion." [Quran 5:3]. 'Umar (R) replied: "No doubt,