Bhagavad Gita Verse 42, Chapter 18

shamo damastapaha shaucham kshaantiraaarjameva cha |
jnyaanam vijnyaanamaastikyam brahmakarma svabhaajavam || 42 ||
 
Restraint of mind and sense organs, penance, purity, forgiveness, and also, knowledge, wisdom and faith, these are the natural duties of a braahman.
 
shamaha : mental restraint
damaha : sensual restraint
tapaha : penance
shaucham : purity
kshaantihi : forgiveness
aaarjam : straightforwardness
eva : also
cha : and
jnyaanam : knowledge
vijnyaanam : wisdom
aastikyam : faith
brahmakarma : duties of a braahman
svabhaajavam : natural
 
Sant Raidas was a cobbler. Sant Tukaram was a farmer. Mirabai was a princess. Sant Namdev came from a family of tailors. Swami Vivekananda was born into an aristocratic family. Sant Chokhamela came from a family that was treated as untouchable. Although all these saints came from different occupations and externally imposed castes, their mental makeup, was that of a braahman. Shri Krishna says that one who is born with, or comes to imbibe, a certain set of qualities and a certain kind of mental makeup, acts according to that mental makeup, and therefore is a braahman.
 
Restraint of mind and senses is seen in actions of braahmans. They never get agitated or perturbed even in the worst of situations. They have an immense capacity to bear and withstand these situations, which comes from leading a life of austerity and penance. Their mind is pure since it does not entertain thoughts of selfishness or hatred. Any mental or physical harm caused by someone else is instantly forgiven. They are extremely straightforward in their dealings with the world, since their mind, speech and actions are in line with each other.
 
Every action performed by a braahmana comes out of knowledge and discrimination. They never perform actions thoughtlessly or carelessly. This knowledge is not purely academic, it becomes wisdom due to the braahman’s ability to apply it to practical situations. Braahmanas also have faith in the teachings of the scriptures, regardless of whether they have learned formally, or have first hand experience of those teachings. Broadly, all these characteristics are the product of a high degree of sattva in the mind, and only a tinge of rajas and tamas.