The story of A?gulim?la is most well-known in the Therav?da tradition. Two texts in the early discourses in the P?li language are concerned with A?gulim?la's initial encounter with the Buddha and his conversion, and are believed to present the oldest version of the story. The first is the Theragath?, probably the oldest of the two, and the second is the A?gulim?la Sutta in the Majjhima Nik?ya. Both offer a short description of A?gulim?la's encounter with the Buddha, and do not mention much of the background information later incorporated into the story (such as A?gulim?la being placed under oath by a teacher). Apart from the P?li texts, the life of A?gulim?la is also described in Sanskrit, Tibetan and Chinese texts. The Sanskrit collection called Sa?yukt?gama from the early M?las?rvastiv?da school, and Chinese translations of this text (translated in the 4th–5th century CE) of the early Sarv?stiv?da and K??yap?ya schools also contain early versions of the story.

Apart from these early texts, there are also later renderings, which appear in the commentary to the Majjhima Nik?ya attributed to Buddhaghosa (5th century CE) and the Theragath? commentary attributed to Dhammap?la (6th century CE). The two commentaries do not appear to be independent of one another: it appears that Dhammap?la has copied or closely paraphrased Buddhaghosa, although adding explanation of some inconsistencies. The earliest accounts of A?gulim?la's life emphasize the fearless violence of A?gulim?la and, by contrast, the peacefulness of the Buddha. Later accounts attempt to include more detail and clarify anything that might not conform with Buddhist doctrine. They also include more miracles, however, and together with the many narrative details this tends to overshadow the main points of the story. The early P?li discourses (Pali: sutta) do not provide for any motive for A?gulim?la's actions, other than sheer cruelty. Later texts may represent attempts by later commentators to "rehabilitate" the character of A?gulim?la, making him appear as a fundamentally good human being entrapped by circumstance, rather than as a vicious killer. In addition to the discourses and verses, there are also J?taka tales, the Milindapañh?, and parts of the monastic discipline that deal with A?gulim?la, as well as the later Mah?va?sa chronicle.

Later texts from other languages that relate A?gulim?la's life include the Avad?na text called Sataka, as well as a later collection of tales called Discourse on the Wise and the Fool, which exists in Tibetan and Chinese. There are also travel accounts of Chinese pilgrims that mention A?gulim?la briefly. In addition to descriptions of the life of A?gulim?la, there is a Mah?y?na discourse called the A?gulim?l?ya S?tra, which Gautama Buddha addresses to A?gulim?la. This is one of the Tath?gatagarbha S?tras, a group of discourses that deal with the Buddha Nature. Apart from textual evidence, early epigraphic evidence has also been found. One of the earliest reliefs found that depicts A?gulim?la dates from approximately 3rd century BCE.

Previous incarnation

The texts describe a previous incarnation before A?gulim?la met the Buddha Gautama. In this life, he was born as a man-eating king turned yaksha (Pali: yakkha, a sort of demon; Sanskrit: yak?a), in some texts called Saud?sa. Saud?sa develops an interest in consuming human flesh when he is served the flesh of a dead baby. When he asks for more, his subjects start to fear for their children's safety and he is driven from his own kingdom. Growing into a monster, Saud?sa meets a deity that promises Saud?sa can retrieve his status as king if he sacrifices one hundred other kings. Having killed 99 kings, a king called Sutasoma changes Saud?sa's mind and makes him a religious man, and he gives up all violence. The texts identify Sutasoma with a previous incarnation of the Buddha, and Saud?sa with a previous incarnation of A?gulim?la.

Youth

In most texts, A?gulim?la is born in S?vatth?, in the brahman (priest) caste of the Gagga clan, his father Bhaggava being the chaplain of the king of Kosala, and his mother called Mant?n?. According to commentarial texts, omens seen at the time of the child's birth (the flashing of weapons and the appearance of the "constellation of thieves" in the sky) indicate that the child is destined to become a brigand. As the father is interpreting the omens for the king, the king asks whether the child will be a lone brigand or a band leader. When Bhaggava replies that he will be a lone brigand, the king decides to let it live.

Buddhaghosa relates that the father names the child Ahi?saka, meaning 'the harmless one'. This is derived from the word ahi?sa (non-violence), because no-one is hurt at his birth, despite the bad omens. The commentary by Dhammap?la states that he is initially named Hi?saka ('the harmful one') by the worried king, but that the name is later changed.

Having grown up, Ahi?saka is handsome, intelligent and well-behaved. His parents send him to Taxila to study under a well-known teacher. There he excels in his studies and becomes the teacher's favorite student, enjoying special privileges in his teacher's house. However, the other students grow jealous of Ahi?saka's speedy progress and seek to turn his master against him. To that end, they make it seem as though Ahi?saka has seduced the master's wife. Unwilling or unable to attack Ahi?saka directly, the teacher says that Ahi?saka's training as a true brahman is almost complete, but that he must provide the traditional final gift offered to a teacher and then he will grant his approval. As his payment, the teacher demands a thousand fingers, each taken from a different human being, thinking that A?gulim?la will be killed in the course of seeking this grisly prize. According to Buddhaghosa, Ahi?saka objects to this, saying he comes from a peaceful family, but eventually the teacher persuades him. But according to other versions, Ahi?saka does not protest against the teacher's command.

In another version of the story, the teacher's wife tries to seduce Ahi?saka. When the latter refuses her advances, she is spiteful and tells the teacher Ahi?saka has tried to seduce her. The story continues in the same way.

Life as a brigand

Following his teacher's bidding, A?gulim?la becomes a highwayman, living on a cliff in a forest called J?lin? where he can see people passing through, and kills or hurts those travelers. He becomes infamous for his skill in seizing his victims.