Here is the story taken from Myokoninden, translated into English by Hisao Inagaki Sensei:
"A warrior named Araki Mataroku lived in Fukui County, Echizen Province. His family belonged to the Jodo school, and he was, from the beginning, a serious seeker of the Way.
When he heard the teaching of Jodoshinshu during the Meiwa era (1764-1772), his stored good karma must have fully ripened. He became the most devoted follower in the district. He continued to say the Nembutsu throughout the day, whether he was walking, standing, sitting or lying down. Even when he was working in the office, his Nembutsu did not stop. Younger warriors ridiculed him, saying that it was an act unbecoming to a warrior.
Mataroku's father, hearing this, asked a priest to give some advice to his son. The priest took the trouble of admonishing Mataroku by quoting the master's words, "Even if one is called a thief of an ox, one should be careful not to be thought of as a pious after-life seeker."
Mataroku respectfully accepted this advice but his gratitude to Amida spontaneously found its expression in the Nembutsu. Since he could not keep the Nembutsu from coming to his lips, he pleaded to the priest, "Master, please make me a special case and allow me to say the Nembutsu as I wish." He then composed two poems:
"Though I try not to say the Nembutsu, it comes to my lips;
In the end people admonish me to stop saying it."
"I have become desperate not knowing what to do;
My Nembutsu is like a burning fire which water cannot put out."
Those who at first ridiculed Mataroku became impressed by his sincere devotion to the Dharma. Soon there was no one who laughed at him about his Nembutsu."