Bukhari

Chapter of Sahih Bukhari Hadith Number: 2818: «بَابُ الْجَنَّةُ تَحْتَ بَارِقَةِ السُّيُوفِ:»
Relevance between the Chapter and the Hadith:
The words that Imam Bukhari rahimahullah has quoted in the chapter heading are: “Paradise is under the gleams of swords.” Thus, Imam Bukhari rahimahullah has established the chapter heading at this point. «باب الجنة السيوف البارقة» Thus, the attribution of «بارقة» to «سيوف» is in relation to «إضافة الصفة إلى الموصوف», and this is in the meaning of «السيوف البارقة». [شرح الكرماني، ج 12، ص: 177]
Ibn Battal rahimahullah says: This is derived from «بريق», and the meaning of “bareeq” is the flash of lightning. [شرح ابن بطل، ج 5، ص: 21]
Allamah Ibn al-Munir rahimahullah, regarding the relevance between the hadith and the chapter, says:
«لم يترجم على الحديث بلفظه فإما أن يكون لفظ الترجمة فى حديث آخر لم يوافق شرطه فنبه عليه فى الترجمة . . . . .» [المتواري على أبواب البخاري، ص: 158]
Imam Bukhari rahimahullah did not take the chapter heading directly from the words of the hadith here. The reason for this is either that when the sword has a shine and gleams, accordingly, it will also have a shadow. In this way, conformity between the chapter and the hadith is established.
Hafiz Ibn Hajar rahimahullah says:
«وقد أورده بلفظ ”تحت ظلال السيوف“ وكأنه أشار بالترجمة إلى حديث عمار بن ياسر رضي الله عنه فأخرج الطبراني بإسناد صحيح عن عمار بن ياسر انه قال يوم الصفين ”الجنة تحت الالبارقة“.» [فتح الباري، ج 6، ص: 41]
“Imam Bukhari rahimahullah’s chapter heading is derived from the narration which Tabarani has transmitted with a sound chain from Sayyiduna Ammar bin Yasir radi Allahu anhu, that Sayyiduna Ammar radi Allahu anhu said on the day of the Battle of Siffin:
«الجنة تحت البارقة»
‘Indeed, Paradise is beneath the gleam (of swords).’
Therefore, the chapter heading that he established was not based on a hadith that met his (Bukhari’s) conditions, and the hadith he transmitted was according to his conditions, that Paradise is under the shade of swords. Thus, when the shade of swords is established, then their gleams are also established. From here, the relevance between the chapter heading and the hadith is clarified.”

Hadith Commentary:
➊
At the time of battle, the swords of both parties come together and cast a shadow.
When two enemies enter the battlefield with swords, the shadow of each other's swords falls upon the opponent, and each tries to defend himself. This occurs when the battle becomes intense.
➋
Jihad is the very act that is the sole means of Islam’s ascendancy, but the Shariah has prescribed certain principles and regulations for it.
The details of these will be mentioned later.
From one narration, it is understood that the Messenger of Allah (sallallahu alayhi wa sallam) narrated this hadith on the day of the Battle of the Trench (Ghazwah Khandaq).
(Fath al-Bari: 6/43)