Varna

Varna (वर्ण varṇa) is a Sanskrit term derived from the root vrn meaning "to choose from".

One of the foremost Rishi in Rigveda is Vishwamitra, who was a King and Kshatriya by birth. Vyasa was of mixed birth between Parasara, a Brahmin and Sathyavathi (a Soodra, fisher woman). Maharishi Matanga was from the Matanga Bhil tribe but was raised as a Brahmana. Hence to attribute inherited class system to Hindu scriptures is without substance. Only Manu Smriti talks clearly about the classes and their duties.
There is an Upanishadic story of a boy who went to a guru to study the various holy Hindu scriptures. His guru asked him what his varna was. Consulting his mother, who was actually a prostitute who didn't really know what her varna was, the boy returned to the guru and told him that he was all the varnas. He worshipped the Gods, thus fulfilling the duties that are ordinarily a Brahmin's, he earned his keep like a Vaishya, took care of cleaning the house, like a Shudra, and protected his family's interest like a Kshatriya. The guru was pleased and told the boy he was fit to be taught and initiated into the Brahmin's life.
Many Hindu yogis and sages have, over the centuries, constantly commented about inheriting social status. Shri Chaitanya Mahaprabhu (15th century), the powerful bhakti of Krishna also denounced inheriting social status. He famously distributed the Hare Krishna mantra to non-brahmins all around India, claiming this was the True path to moksha.
Kanakadasa of the 15th century also denounced inherited social status. He believed that Life in every human being is Divine, and that only the ignorant wrought injustice against their own brethren by this practice. Basavanna of the 12th century is said to have denounced inherited social status and tried to unify all communities under the Linga (form of Shiva).

MANU SMIRITI is often quoted in reference to the Varna system as an inherited social class system. The Manu Smriti is a later work that does not form a part of Hindu Scriptures, so it is of questionable relevance. Use of the Manu Smriti by the British colonialists has been used by politicians and sociologists to denigrate those of the Hindu faith.[1].
In the religious scripture Mahabharata, Yudhisthira, is questioned by Yama in the form of a Yaksha, about what makes one a Brahmin. Yudhisthira, without hesitation, said that it is conduct alone that makes one a Brahmin.
The late Swami Krishnananda, a foremost disciple of Swami Sivananda and former General Secretary of Divine Life Society, noted the following about inherited social status in his autobiography:"While the [varna] system was originally evolved for the necessary classification of human duty in order to preserve the organic stability of society, its original meaning and its philosophical foundation was forgotten through the passage of time, and bigotry and fanaticism took its place through the preponderance of egoism, greed and hatred, contrary to the practice of true religion as a social expression of inner spiritual aspiration for a gradual ascent, by stages, to God Almighty. Vidura, famous in the Mahabharata, was born of a Shudra woman. But he had the power to summon the son of Brahma, from Brahmaloka, by mere thought. Which orthodox Brahmin can achieve this astounding feat? It is, therefore, necessary for everyone to have consideration for the facts of world-unity and goodwill, Sarvabhuta-hita, as the great Lord mentions in the Bhagavad Gita. Justice is more than law. No one's body is by itself a Brahmin, because it is constituted of the five gross elements,- earth, water, fire, air and ether. Else, it would be a sin on the part of a son to consign to flames the lifeless body of a Brahmin father. It is, therefore, not proper to victimise a colleague by an action plan of any religious community wedded to fundamentalist doctrines."[2]
Atri's statement is famous. "By birth every one is a shudra, by samskars he becomes a Dvija (i.e., twice-born). By learning (studying Vedas), he becomes a Vipra and by realizing Brahman, he attains the status of a Brahmana" (Janmana jayate ....etc.)