Sahih al-Bukhari 2443
صحيح البخاري#2443Sahihحَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا هُشَيْمٌ، أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ أَبِي بَكْرِ بْنِ أَنَسٍ، وَحُمَيْدٌ الطَّوِيلُ، سَمِعَا أَنَسَ بْنَ مَالِكٍ ـ رضى الله عنه ـ يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " انْصُرْ أَخَاكَ ظَالِمًا أَوْ مَظْلُومًا ".
Narrated Anas bin Malik:Allah's Messenger (ﷺ) said, "Help your brother, whether he is an oppressor or he is an oppressed one
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 46:4