Bukhari

Hadith Commentary:
In this verse, Allah Almighty swears by His own Self and declares that the faith of these people will never be complete until they make you (O Prophet) the judge in their disputes, and then, after hearing your decision, they accept it wholeheartedly and with happiness.

This is the very sign of a believer: that in any matter, if an authentic hadith is found, he immediately begins to act upon it with joy and contentment.

Even if all the scholars and mujtahids (jurists) of the world unite and speak against it, let them do so; not even for a moment should he entertain the thought in his heart that it is not a good thing to abandon the school of these mujtahids. Rather, his heart should be filled with great happiness and delight that Allah, the Most High, granted him the ability to follow the noble hadith and delivered him from the snares of Kidan and Qahistan.

(Wahidi)

Hadith Commentary:
1.
The aforementioned law is not only for the hypocrite but for the entire Ummah and for all times until the Day of Judgment.
The law is that any Muslim who is not prepared to wholeheartedly accept the statement, command, or decision of the Messenger of Allah (sallallahu alayhi wa sallam) and to submit before it, is not a Muslim at all.
The statements and decisions of the Messenger of Allah (sallallahu alayhi wa sallam) are present in the books of hadith; now, whoever gives preference to the statement of any other ruler, scholar, spiritual guide, or imam over them, will also fall under this same warning.
This noble verse is a guide and criterion for us in deciding all disputes and disagreements of the Ummah.
The sign of a believer is that when he finds an authentic hadith regarding an issue, he happily begins to act upon it.
2.
Apparently, from the noble verse it seems that whoever, despite considering another law to be false, turns towards it, is not a Muslim; or if someone, despite considering a Shari'ah decision to be true, feels constriction in his heart, then he too is not a Muslim. However, since a person has no control over constriction of the heart, the answer is that there are three levels of arbitration, absence of discomfort, and submission as follows:
➊. Belief (I'tiqad):
This is called faith (iman). If this is absent, then with Allah it is disbelief (kufr), and the one who commits it is also a disbeliever (kafir).
➋. Speech (Lisan):
This is called affirmation (iqrar).
If there is no affirmation, then in the eyes of people he is a disbeliever (kafir).
➌. Action (Amal):
This is called piety (taqwa) and reform (islah). If this is absent, then there will be sinfulness (fisq).
Since the noble verse mentions the hypocrites, the intended meaning is the first level, i.e., that there is no confirmation of faith and its truth in the heart regarding it.
This takes a person out of the fold of Islam.
3.
It should be clear that the first ruling which the Messenger of Allah (sallallahu alayhi wa sallam) gave to Zubair (radi Allahu anhu) was based on reconciliation and harmony, and the second ruling, in which Zubair (radi Allahu anhu) was given his full right, was in accordance with the demands of justice and fairness.
In reality, the Ansari leveled a grave accusation against you, claiming that the Messenger of Allah (sallallahu alayhi wa sallam), out of courtesy and consideration, could never act justly. On this basis, a severe warning is mentioned in the noble verse.
It is also possible that the Ansari was sincere but did not know that in every minor and major matter, obedience to the Messenger of Allah (sallallahu alayhi wa sallam) is obligatory upon them; therefore, a warning is given in the noble verse.
And Allah knows best.

Hadith Commentary:
It is understood from this that to submit oneself without any objection or reservation before the decision of the Prophet (sallallahu alayhi wa sallam) is itself the proof of faith. If even the slightest constriction is felt in the heart regarding this, then only Allah can safeguard such a person’s faith.

Those rigid followers (muqallidīn jāmidīn) should reflect who, on the basis of mere sectarian prejudice, stand obstinately in opposition to an authentic hadith.

And they reject the decision of the Prophet (sallallahu alayhi wa sallam); with what face will these people present themselves before him at the Pond of Kawthar?

Hadith Commentary:
(1)
Landowners know that for an orchard, enough water is accumulated so that it is absorbed and reaches the roots of the trees.
It is evident that to accumulate this much water, it must be held back for a while.
To irrigate one’s orchard with water and to hold back the water of a rain-fed stream is first the right of the one whose orchard or field is in the upper area.
(2)
No one should obstruct the water of large rivers.
Everyone has the right to take water from them whenever, however, and as much as they wish.
This ruling pertains to the water flowing from rain-fed streams and valleys: those upstream should use the water first and then leave it for those downstream; there is no disagreement in this matter.

Hadith Commentary:

Thus, as a legal principle, it was established that the field being filled with water up to the ankles constitutes its being irrigated.

Hadith Commentary:
(1)
The initial judgment given by the Messenger of Allah (sallallahu alayhi wa sallam) was in accordance with the customary practice of that time, and he adopted a middle course in which consideration was given to the neighbor. However, when the Ansari was not satisfied with this and even expressed displeasure, the Prophet (sallallahu alayhi wa sallam) granted the full right to Zubair (radi Allahu anhu).

(2)
When people observed that the length and width of embankments and walls varied, in view of the incident that occurred, the amount up to the ankles was fixed. The purpose is that the owner of the upper field has the right to water to the extent that it suffices for the roots of his crop, then he will leave that water for the one below; the water will proceed in this order until it is finished. Thus, as a legal principle, it was established that the filling of water in the field up to the ankles constitutes its irrigation.

(3)
It is also understood from this that submitting without any objection to the decision of the Messenger of Allah (sallallahu alayhi wa sallam) is itself a sign of faith. If one feels even the slightest constriction in the heart regarding it, then there is no good in his faith, meaning his heart is devoid of faith.

Benefit:
By "the one above" is meant the person whose land receives the floodwater first.
And by "the one below" is meant the person whose land receives the water later.
When so much water has accumulated in the field that it reaches a man's ankles, then he should allow the other person to irrigate his field.