Fundamental Rights
(1) There shall be equality of opportunity for all citizens in matters relating to employment or appointment to any office under the State. (2) No citizen shall, on grounds only of religion, race, caste, sex, descent, place of birth, residence or any of them, be ineligible for, or discriminated against in respect of, any employment or office under the State. (3) Nothing in this article shall prevent Parliament from making any law prescribing a residence requirement for certain classes of employment or appointment within a State or Union territory. (4) Nothing in this article shall prevent the State from making any provision for the reservation of appointments or posts in favour of any backward class of citizens which, in the opinion of the State, is not adequately represented in the services under the State. (4A) Nothing in this article shall prevent the State from making provision for reservation in matters of promotion, with consequential seniority, for the Scheduled Castes and Scheduled Tribes which are not adequately represented in the services under the State. (4B) Unfilled reserved vacancies of a year may be carried forward and filled in a later year as a separate class, without being counted against the 50% ceiling on reservation for that later year. (5) Nothing in this article affects a law requiring the head of a religious or denominational institution to belong to a particular religion or denomination. (6) Nothing in this article shall prevent the State from making provision for the reservation of posts in favour of economically weaker sections of citizens, in addition to existing reservation, subject to a maximum of ten per cent of the posts in each category.
Every citizen gets an equal shot at government jobs - the government cannot reject your application for a public-sector job purely because of your religion, caste, sex, or where you live (with narrow, specifically-permitted exceptions like certain residence requirements Parliament may set, and religious-institution roles). This article also specifically permits reservation systems for backward classes, SCs, STs, and economically weaker sections to correct historical under-representation.
If a state-run public sector undertaking rejects a qualified candidate for a clerical post solely because of their caste (outside any lawful reservation policy), that is a direct violation of Article 16(2) that can be challenged before the appropriate tribunal or court.