Bukhari

Hadith Commentary:
In this hadith, shirk (associating partners with Allah) has been described as the greatest of the major sins (akbar al-kabair), and the reality is indeed this: Allah, the Exalted, has declared Paradise forbidden for the polytheist, as is stated in the Word of Allah:

“Whoever associates partners with Allah, Allah has made Paradise forbidden for him, and his abode is the Fire.” ( al-Ma’idah 5:72)

From some narrations, it is understood that murder is considered the greatest of the major sins, and adultery (zina) is regarded as a very grave sin. In reality, in every context, the hadith is mentioned according to its requirement and in accordance with the state of the audience present. In any case, there is no doubt regarding shirk being the greatest of the major sins.

(‘Umdat al-Qari: 16/195)

Hadith Commentary:
You were experiencing difficulty in repeatedly stating this, and out of compassion, the Companions wished that you would not have to bear the hardship of repeating it again and again.
They remained silent while you had already stated it several times.
The scholars have divided sins into two categories: minor (saghirah) and major (kabirah), for which there are many evidences.
Some hold the view that there is no such thing as a minor sin; all sins are major.
Imam Ghazali (rahimahullah) states:
"To deny the distinction between major and minor sins is not befitting for a jurist (faqih)."
That is, it is not appropriate for those who possess understanding of the religion to deny the difference between major and minor sins.
The Prophet (sallallahu alayhi wa sallam) mentioned false testimony repeatedly because it is a very grave sin,
and a precursor to many evils. His purpose was that Muslims should never commit it.

Hadith Commentary:
(1)
By "kabair" (major sins) are meant those very grave sins from which the Shariah has prohibited, and for the commission of which a very severe warning has been given. In these ahadith, four major sins have been identified. Among them, the fourth sin, which the Prophet (sallallahu alayhi wa sallam) mentioned after he was reclining and then sat up, is: "It is the sin of false testimony."

(2)
In courts, the outcome of judgments depends on the statements of witnesses. In such circumstances, by giving false testimony and causing an incorrect judgment, it is as if one is responsible for the destruction of countless families. The Messenger of Allah (sallallahu alayhi wa sallam) emphasized the gravity of false testimony because people are very bold in committing this crime, and its harm encompasses countless people. Therefore, a Muslim should avoid it. In the hadith, only false testimony is mentioned because through it, a right is established for the undeserving and the rightful person's due is destroyed. Likewise, by concealing true testimony, the right of the deserving is also destroyed. Therefore, the mention of one is considered sufficient for the other.

Hadith Commentary: Benefits and Issues:
Opposing Allah, in terms of disobedience, makes every sin a major one. However, in relation to each other, not all sins are equal. Clearly, those sins for which there is a prescribed punishment, or whose sin and crime are severe, or whose harm and negative effects are greater, will be considered major sins. Those whose punishment, severity, harm, and negative effects, or scope of impact, are limited will be considered minor sins.

Takhrij:
«أخرجه البخاري، الشهادات، باب ما قيل في شهادة الزور، حديث:2654، ومسلم، الإيمان، باب الكبائر وأكبرها، حديث:87.»©Explanation:
➊ From this hadith, it is understood that major sins (kabirah) are numerous, for example: associating partners with Allah (shirk), disobedience to parents, fleeing from the battlefield, slandering a chaste woman regarding her honor, and giving false testimony, etc.
➋ According to a narration in the two Sahihs (Sahih al-Bukhari and Sahih Muslim), giving false testimony is not only among the major sins (kabirah) but is included among the gravest of the major sins (akbar al-kabair).
➌ A major sin (kabirah) is that for which the Shari‘ah has prescribed a punishment or for which there is a warning of punishment in the Hereafter.
➍ If the practice of giving false testimony in courts were to cease, justice would become extremely accessible and swift.
The root of corruption in the judicial system is false testimony and bribery.
If this system is purified from these two great evils, then the society will experience the blossoming of peace and security.