Ajatasattu was the son of Bimbisara, the king of Magadha state, a devoted follower of the Buddha. Prior to the birth of the prince, the queen had the desire to drink the blood from the right arm of the king. When the king learnt this, he had the blood taken out and fulfilled her desire. The soothsayers then predicted that the child in the queens womb would become the kings enemy. Hence the name Ajatasattu - the potential enemy of the father while still in the mothers womb.
The queen tried to abort the child but as the kings kamma and the childs kamma would have it otherwise, she did not succeed in her attempt. The king had her pregnancy well protected and the child was born. When he came of age, he was appointed heir apparent.
Then the young prince fell into the clutches of the evil minded Devadatta who misused his psychic power for his selfish ends. Turning himself into a boy with a snake coiled around his waist, he appeared before Ajatasattu and then showed himself as a bhikkhu. The prince was deeply impressed, and no wonder for people are very much interested in miracles and they have blind faith in anyone who can perform them. The prince held Devadatta in high esteem and became his devoted follower.
Then Devadatta made another move for the success of his evil design. He told the prince that since people did not live long, he (the prince) should kill his father and become king while still in the prime of his life; and that he (Devadatta) on his part would kill the Buddha. The prince failed in his attempt on the life of the king but when the latter learnt of his desire, he handed over his kingship to his son.
The transfer of power nonetheless came short of Devadattas scheme. On his advice, Ajatasattu imprisoned his father and starved him. The queen was the only person who was permitted to visit the prison and see the king. She secretly brought food for the king by various means and at last she was forbidden to visit the prison. From that day, the king got nothing to eat but still he managed to keep himself in good physical condition by pacing on the floor. Then by the kings order, the barbers caused such injury to the feet of his father as to make it impossible for him to walk. According to the commentary, he was thus injured because in a previous life he walked with footwear on the platform of a pagoda and trod with unwashed feet on a mat meant for the bhikkhus.
King Bimbisara died probably at the age of 67. His son Ajatasattu was not evil minded at heart. His good nature was evident in his devotion to the Buddha after he had wronged his father, his adoration and enshrinement of the Buddha relics and whole hearted support which he gave to the First Council. It was his association with the evil teacher that led him astray to the point of patricide. His life affords us a lesson that we should specially bear in mind.
On the very day of his fathers death, his wife gave birth to a son. On hearing the news, he became excited and overwhelmed with great affection for his child. This reminded him of his father and he ordered the release of the imprisoned king, but it was too late. When later on he learnt from his mother how much he was loved and cared for by his father in his childhood, he was seized with remorse. His life became wretched and miserable. He could not sleep at night, haunted by the visions of hell and smitten by conscience for his crime against his father, a devout lay disciple of the Buddha at that.
So led by the physician Jivaka, he went to see the Buddha. At that time the Lord was surrounded by over a thousand bhikkhus. But as they were in a contemplative mood, all was quiet with none speaking or making any movement of their hands or feet. Being deeply impressed, the king said, “May my son Udayabaddha be blessed with the kind of serenity which these bhikkhus possess!” Perhaps he feared lest his son should come to know how he seized power and try to follow in his fathers footsteps. But later his fear did become a reality for down to his great grandson, the sons ascended the throne after killing their fathers.
King Ajatasattu asked the Buddha about the immediate benefits of the life in the holy order. The Lord enlarged on the benefits accruing from the holy life - the lay followers reverence for the bhikkhu, moral purity, the first jhana and other higher states of consciousness in the mundane sphere, psychic powers, extinction of defilements and the attainments of the holy path.
After hearing the sermon, Ajatasattu formally declared himself a disciple of the Buddha. He would have attained the first stage on the path but for his patricide. Nevertheless, from that time he had peace of mind and after his death, he was spared the terrors of Avici hell that would have been in store for him had he not met the Buddha.