Oath/ Affirmation binds the designated authority to do his duties well and to be faithful to the constitution. As the President – The President is the head of the state and all functions of the country are performed in his name. His ordinance making power confers him the role of a legislator. He also has got judicial powers of pardoning, and he is the supreme commander of the Armed forces.
President – Article 60 which provide the form of oath or affirmation of the president requires him to preserve, protect and defend the constitution and law at his best ability. Also he is required to devote himself to the service and well-being of the people of India.
Minister – He belongs to political parties and he is subjected to pulls and pressures of Political ups and downs. Hence he is required, on an oath or affirmation, to discharge his duties without fear or favor, affection or ill-will. In the midst of political activities, he is very much required to keep secrecy of official matters.
Legislator – He is to make laws and solve the problems of national or local importance arising day to day. They need to discharge this duty faithfully on oath.
Judicial members – They are to uphold the constitution and law of the country. They take oath to this effect and accept duties to perform them with best ability, knowledge and judgement. They are expected by oath to discharge these duties without fear or favor, affection or ill-will.
Hence the functions and responsibilities of the President, the Ministers, the Legislators and the members of the Judiciary are specific and different from each other, the forms of oath are also different accordingly. However all these are commonly obliged to bear true faith and allegiance to the constitution and to uphold sovereignty and integrity of India on oath.