Bukhari

Hadith Commentary:
➊
Imam Bukhari rahimahullah has used this hadith as evidence for the increase and decrease of faith (iman), because in it, five things are declared as the foundations of Islam, and these five things are not found in every person. Some do not perform prayer (salah), some do not give alms (zakat), some are negligent regarding pilgrimage (hajj), and some show laxity concerning fasting (sawm).
In this respect, there is also variation in the ranks of faith.
Someone’s Islam is deficient, and in some, these signs are found in full, which shows that there is zeal in his heart.
If there is no adherence to these actions, then this is a sign of deficiency in his religion.
It should be clear that, according to the hadith scholars (muhaddithin), Islam and faith (iman) are two names for the same reality; thus, faith also applies to these five things. Therefore, it is known that faith is composite and subject to increase and decrease.

➋
At this point, jihad is not mentioned among the five pillars, even though it holds great importance in the religion of Islam. This is because jihad is a communal obligation (fard kifayah), which, in specific circumstances, becomes an individual obligation (fard ayn). Also, in this hadith, there is no mention of belief in other prophets and angels along with the testimony of faith (kalimah shahadah), because affirmation of the Messenger of Allah sallallahu alayhi wa sallam is, in essence, affirmation of all the prophets, and the foundation of the other principles of faith is also that the Messenger of Allah sallallahu alayhi wa sallam’s prophethood is accepted wholeheartedly.
(: Fath al-Bari 1/29)

➌
This hadith also has a reason for its narration.
That is, Abdullah ibn Umar radi Allahu anhuma narrated this hadith in response to an objection from a man named Hakim.
Its explanation is as follows: He came to Abdullah ibn Umar radi Allahu anhu and said:
“O Abu Abdur-Rahman! What is the reason that one year you perform hajj and the next year you perform umrah, but you have abandoned jihad, even though you are well aware of its importance?” In response, he said that the foundation of Islam is upon five things, and jihad is not mentioned among them.
(: Sahih al-Bukhari, Tafsir, Hadith: 4514)

➍
Although affirmation of the heart (tasdiq al-qalb) is not mentioned in the hadith, the word “shahadah” (testimony) necessitates it, because shahadah refers to a statement that is in accordance with the heart.
After shahadah, several actions are mentioned.
Among them, prayer (salah) and alms (zakat) are derived from Allah’s attribute of majesty (jalal), which requires that they be performed with utmost respect; even a slight negligence can shatter this delicate vessel. Likewise, pilgrimage (hajj) and fasting (sawm) reflect Allah’s attribute of beauty (jamal).
This requires that they be performed with passion and fervor, and this aspect also demands that, turning away from others, one’s full attention be directed toward the intended purpose.
In hajj, there is repentance to Allah, and in fasting, there is turning away from others.

➎
In this narration, hajj is mentioned before fasting in Ramadan.
Imam Bukhari rahimahullah, considering this narration as the original, has mentioned the chapters of hajj before the chapters of fasting in his book, whereas in some narrations from Abdullah ibn Umar radi Allahu anhu, fasting in Ramadan is mentioned before hajj.
(: Sahih Muslim, Iman, Hadith 111(16))
Hafiz Ibn Hajar rahimahullah, considering the aforementioned narration of Sahih Muslim as the original, has called the narration of Sahih Bukhari a transmission by meaning (naql bil-ma’na), because in one narration of Muslim, when Sa’d ibn Ubaydah narrates from Abdullah ibn Umar radi Allahu anhu, fasting in Ramadan is mentioned before hajj.
There is further clarification in it that when a man in the gathering changed the order and said, “hajj and fasting in Ramadan,” Abdullah ibn Umar radi Allahu anhu replied, “No, rather the words of the hadith are that fasting in Ramadan comes before hajj; I heard it from the Messenger of Allah sallallahu alayhi wa sallam in this way.”
(: Sahih Muslim, Iman, Hadith: 111(16))
In one narration of Sahih Bukhari, fasting in Ramadan is mentioned before hajj, and even before the giving of zakat.
(: Sahih al-Bukhari, Tafsir, Hadith 4514)
According to one narration of Bukhari, when Ubaydullah ibn Musa narrates from Hanzalah, hajj is mentioned before fasting in Ramadan, but according to the narration of Sahih Muslim, when Abdullah ibn Numayr narrates from him, fasting in Ramadan is mentioned before hajj.
(: Sahih Muslim, Iman, Hadith: 114(16))
When there is explicit mention of hearing (tasrih sama’) in the narration of Sahih Muslim, and this narration of Hanzalah also agrees with the fundamental narration, then there is no harm in calling the narration of Sahih Bukhari a transmission by meaning (naql bil-ma’na).
However, this answer is certainly contrary to the lofty status of Imam Bukhari rahimahullah, because he, based on this very narration of Abdullah ibn Umar radi Allahu anhuma, has mentioned the chapters of hajj before the chapters of fasting. Also, when his son Zayd ibn Abdullah narrates from Abdullah ibn Umar radi Allahu anhuma, he too mentions pilgrimage to the House (hajj al-bayt) before fasting in Ramadan, as is in Sahih Muslim, Iman, Hadith 16.
In addition, when Sa’d ibn Tariq narrates from Sa’d ibn Ubaydah, he too mentions hajj before fasting in Ramadan.
(: Sahih Muslim, Iman, Hadith 112(16))
It is also possible that Abdullah ibn Umar radi Allahu anhuma heard it both ways from the Messenger of Allah sallallahu alayhi wa sallam, but Hafiz Ibn Hajar rahimahullah has refuted this position.
(: Fath al-Bari: 1/71)

Hadith Commentary:
1.
The supporters of the government tried to argue before Abdullah ibn Umar (radi Allahu anhu) from a Qur'anic verse that fighting against rebellious Muslims is permissible.
Since you are a great personality, you can play an influential role in this matter.
In contrast, Abdullah ibn Umar's (radi Allahu anhu) position was that fighting against rebellious people requires numbers and preparation.
I do not have the men and weapons to fight them, so I have chosen the path of silence and acceptance, withdrawing myself. As for the eradication of discord (fitnah), we had already destroyed it in the blessed era of the Messenger of Allah (sallallahu alayhi wa sallam).
Now, only fighting for the seat of power and authority remains, and I have nothing to do with that.
2.
This Khariji equated this war among Muslims with jihad against the disbelievers.
Although fighting against rebellious Muslims is permissible, it is by no means equal to jihad against the disbelievers.
In any case, Abdullah ibn Umar (radi Allahu anhu) remained steadfast on his position until the end, so much so that even at the request of his sister, Umm al-Mu'minin Hafsa (radi Allahu anha), he did not participate in the incident of arbitration (tahkim).

(1) The purpose of the chapter is to mention those pillars and fundamentals of Islam upon which the entire structure of Islam is established. And they are only five: the first and most virtuous pillar among them is bearing witness to the testimony of Tawhid (the oneness of Allah). This is the most virtuous because as long as a disbeliever does not bear this testimony, he remains a disbeliever and cannot become a Muslim. To become a Muslim, it is necessary to verbally affirm the testimony of faith (shahadah). Then, in the second place, is prayer (salah). This is obligatory upon every rich and poor, male and female.

(2) The implication of the answer is that jihad is not among the individual obligations (fard ayn), but rather it is a collective obligation (fard kifayah), the fulfillment of which is the responsibility of the government of the time. The government may assign as many individuals to this task as it deems appropriate. When, according to the need, individuals are appointed to this task and are fulfilling the duty of national defense, then it is not necessary for the general public to participate in jihad; they may continue with their other tasks. However, it is a virtue: if a person, after fulfilling his obligations, participates in jihad with the permission and consent of the government of the time and the relevant family members, he will attain virtue.

(3) These are the five pillars of Islam, that is, they are individual obligations (fard ayn). Without fulfilling the two testimonies (shahadatayn), no person can enter Islam at all. Prayer (salah) is also obligatory upon every adult and sane person for their entire life; no one is exempt from it. Zakat is obligatory upon every wealthy person who possesses wealth in excess of his needs. (Details have already been mentioned previously.) Hajj is obligatory upon every person who can easily reach the House of Allah (Baytullah) and possesses the expenses for the journey and return. Fasting in the blessed month of Ramadan is obligatory upon every sane and adult person. If there is an excuse, making up the fasts (qada) becomes obligatory, and if one is unable to fast at all, then expiation (fidya) becomes obligatory.

(4) The mention of fasting in Ramadan comes at the end because it is a passive act of worship (in this, nothing is actively done), otherwise, in terms of importance, its rank is after prayer. In any case, like prayer, it is a physical act of worship.

(5) In the translation, the phrase with "wa" (and) is explicitly mentioned in other chains of this hadith. Without it, the testimony of faith (shahadah) is not valid.

Takhrij al-Hadith:
[صحيح بخاري 8],
[صحيح مسلم 16]

Fiqh al-Hadith
➊ From this hadith, it is understood that Islam and Iman (faith) are, in essence, two names for the same thing. A distinction is also made between Islam and Iman in such a way that Islam refers to a person's outward state, while Iman refers to the inward (belief-based) state. The statement of Allah, the Exalted, is: «قَالَتِ الْأَعْرَابُ آمَنَّا قُلْ لَمْ تُؤْمِنُوا وَلَـكِنْ قُولُوا أَسْلَمْنَا وَلَمَّا يَدْخُلِ الْإِيمَانُ فِي قُلُوبِكُمْ» "The Bedouins say: 'We have believed.' Say: 'You have not believed; rather, say: We have submitted (become Muslims), for faith has not yet entered your hearts.'" [49-الحجرات:14]

➋ Among the Salaf Salihin (pious predecessors), there is a difference of opinion regarding the takfir (declaring as disbeliever) of one who abandons the prayer (salat). The majority are of the view that such a person is to be declared a disbeliever. Considering the Islamic texts, the correct and well-researched position is that whoever completely abandons prayer, not performing it at all, is a disbeliever (kafir). However, one who sometimes performs it and sometimes does not, such a person is not a disbeliever, but is certainly a grave sinner and a transgressor (fasiq). His action is an act of disbelief (kufr), and the caliph of the Muslims may enforce disciplinary punishment (ta'zir) upon him. There is consensus that whoever denies the obligation of prayer, zakat, fasting in Ramadan, or Hajj is a disbeliever and outside the fold of the Muslim community.