Shuddhi Movement was started by Arya Samaj in earlier part of 20th century to bring back the people who transformed their religion to Islam and Christianity from Hinduism. The literal meaning of Shuddhi is purification but Arya Samajis didn’t aim at literal meaning rather they meant reconversion by the term.
There was vast difference in the scriptural authorities of these religions as Islam and Christianity claimed divine authority for their Koran and Bible respectively while Vedas of Hinduism didn’t put up such claims.
Founder of Arya Samaj, Dayananda then strived to give the Vedas the similar degree of supernatural authority. This process of reconverting Hindus from Islam and Christianity was accompanied by a Sanghathan movement.
Shuddhi had a social reform agenda behind its rationale and was aimed at abolishing the practise of untouchability by converting outcasts from other religions to Hinduism and integrating them into the mainstream community by elevating their position, and instilling self-confidence and self-determination in them. The movement strove to reduce the conversions of Hindus to Islam and Christianity, which were underway at the time.
In 1923, Swami Shraddhanand founded the 'Bhartiya Hindu Shuddhi Mahasabha' (Indian Hindu Purification Council) and pushed the agenda of reconversion, which eventually created a flashpoint between Hindus and Muslims as Hindus were the recipients of the violence.. Mahatma Gandhi made a comment on Swami Shraddhananda in an article titled 'Hindu-Muslim-Tensions: Causes and Resistance' in the May 29, 1922 issue of Young India.