Bukhari

Hadith Commentary:
‘Asfan is a place 36 miles from Makkah; the watermelons of this area are famous.
Although the Prophet (sallallahu alayhi wa sallam) himself did not perform tamattu‘, he nevertheless commanded others to do so, so it is as if he himself did it.
Here, an objection arises: the discussion was about tamattu‘, so why did Ali (radi Allahu anhu) perform qiran? What does this mean?
The answer is that both qiran and tamattu‘ have the same ruling.
Uthman (radi Allahu anhu) considered both to be impermissible.
It is strange, for it is clearly mentioned in the Noble Qur’an:
﴿فَمَنْ تَمَتَّعَ بِالْعُمْرَةِ إِلَى الْحَجِّ﴾ ()
and there are numerous authentic hadiths from multiple Companions,
from which it is established that the Prophet (sallallahu alayhi wa sallam) commanded tamattu‘.
Then, it is difficult to understand why these individuals prohibited it.
Some have said that ‘Umar (radi Allahu anhu) and ‘Uthman (radi Allahu anhu) prohibited this tamattu‘ in the sense that, after intending Hajj, one would annul it and turn it into ‘umrah.
However, this too is explicitly established from the hadiths.
Some have said that this prohibition was in the form of discouragement (tanzih),
meaning they considered tamattu‘ to be contrary to virtue.
This too is not correct,
because it is clearly established from the hadith that tamattu‘ is the most virtuous.
In summary, this is a difficult issue, and this is why ‘Uthman (radi Allahu anhu) could not give any answer in response to ‘Ali (radi Allahu anhu).
In this regard, Hafiz (rahimahullah) says:
فِي قِصَّةِ عُثْمَانَ وَعَلِيٍّ مِنَ الْفَوَائِدِ إِشَاعَةُ الْعَالِمِ مَا عِنْدَهُ مِنَ الْعِلْمِ وَإِظْهَارُهُ وَمُنَاظَرَةُ وُلَاةِ الْأُمُورِ وَغَيْرِهِمْ فِي تَحْقِيقِهِ لِمَنْ قَوِيَ عَلَى ذَلِكَ لِقَصْدِ مُنَاصَحَةِ الْمُسْلِمِينَ وَالْبَيَانُ بِالْفِعْلِ مَعَ الْقَوْلِ وَجَوَازُ الِاسْتِنْبَاطِ مِنَ النَّصِّ لِأَنَّ عُثْمَانَ لَمْ يَخْفَ عَلَيْهِ أَنَّ التَّمَتُّعَ وَالْقِرَانَ جَائِزَانِ وَإِنَّمَا نَهَى عَنْهُمَا لِيُعْمَلَ بِالْأَفْضَلِ كَمَا وَقَعَ لِعُمَرَ لَكِنْ خَشِيَ عَلِيٌّ أَنْ يَحْمِلَ غَيْرُهُ النَّهْيَ عَلَى التَّحْرِيمِ فَأَشَاعَ جَوَازَ ذَلِكَ وَكُلٌّ مِنْهُمَا مُجْتَهِدٌ مَأْجُورٌ۔
(Fath al-Bari)
That is, in the aforementioned incident of ‘Uthman and ‘Ali (radi Allahu anhuma) there are many benefits.
For example, whatever knowledge a person possesses, he should spread it, and for the well-being of the Muslims, he should express the truth, even if it comes to the point of debating with Muslim rulers; this too should be done.
And not only should the truth be stated, but it should also be demonstrated through action, and deriving a ruling from the text is permissible.
Because this matter was not hidden from ‘Uthman (radi Allahu anhu): both Hajj tamattu‘ and qiran are permissible, but he prohibited tamattu‘ out of consideration for acting upon what is more virtuous,
just as occurred with ‘Umar (radi Allahu anhu), and ‘Ali (radi Allahu anhu) interpreted it as such, lest the general public take this prohibition as being one of unlawfulness.
Therefore, he expressed its permissibility and even demonstrated it through action.
Thus, both of them are mujtahids and both will be rewarded.
From this, it is also evident that if a subsidiary (furu‘i) difference occurs with good intention, one should not speak ill of one another because of it.
Rather, one should act upon one’s own research and leave the matter of the other to Allah.
Such differences in understanding in subsidiary matters are natural,
for which there are hundreds of examples among the pious predecessors (salaf salihin).
But, alas, the less knowledgeable scholars of the present age have made such differences into mountains out of molehills, thereby destroying and ruining the Ummah.
O Allah, have mercy on the Ummah of Your beloved.

Hadith Commentary:
(1)
Did Ali (radi Allahu anhu) enter into ihram for Hajj Qiran while he had a disagreement with Uthman (radi Allahu anhu) regarding Hajj Tamattu'? The answer is that Uthman (radi Allahu anhu) used to prohibit both Hajj Tamattu' and Qiran, as is mentioned in Hadith: 1563.
(2)
Uthman (radi Allahu anhu) prohibited it so that people would not neglect Hajj Ifrad, meaning his disagreement was not about permissibility or impermissibility, but rather about what is superior and what is less superior.
In one narration, there is an addition that Uthman (radi Allahu anhu) prohibited Hajj Tamattu', but when Ali (radi Allahu anhu) and his companions entered into ihram for 'Umrah, Uthman (radi Allahu anhu) did not prohibit them.
Ali (radi Allahu anhu) said to him:
"Do you know that the Messenger of Allah (sallallahu alayhi wa sallam) performed Tamattu'?" Uthman (radi Allahu anhu) replied:
"Yes, I know, but at that time we were in a state of fear."
(Sahih Muslim, Al-Hajj, Hadith: 2962 (1223))