He met with Mahatma Gandhi in 1915 and was inspired. He decided to get involved full-time in the freedom struggle and gave up his legal practice. He was instrumental in Gandhi taking up the Champaran and Kheda Satyagraha, in which Gandhi handpicked Rajendra Prasad and Anugrah Narayan Sinha along with him to successfully lead the movement. Gandhi was so impressed by Prasad's dedication that he set aside a full chapter on him in his autobiographical book, "The Story of My Experiments with Truth", called "The Gentle Bihari".