Help Your Brother, Whether He is Oppressor or He is an Oppressed One

Narrated Anas(R.A) :
Allah's Apostle(Salla Allahu Alyhe Wa Aalihe Wassalam ) said,

"Help your brother, whether He is oppressor or he is an oppressed one.
People asked,
"O Allah's Apostle! It is all right to help him if he is an oppressed, but how should we him if he is an oppressor?"
The Prophet said,
"By preventing him from oppressing others."

Sahih Al-Bukhari
Volume :3
Book :43 (Oppressions)
Hadith :624