The story of King Shrenik and Anathi Muni is a Jain dharmakatha used to explain the Āśharaṇa-bhāvanā (अशरण भावना – contemplation of helplessness / lack of real refuge).

In terms of source:

1. Not from main Āgams directly

- This incident is not found as a full narrative in the primary canonical Āgams (like Ācārāṅga, Sūtrakṛtāṅga, etc.). - It is a later narrative based on the lives of Bhagwān Mahāvīr’s time (King Shrenik / Bimbisār and the monks), used by ācāryas to teach bhāvanās.

1. Commonly found in bhāvanā-granths and story collections

- The story appears in Bhāvanā–Bodh / Bhāvanā–Pāṭh type texts under Āśharaṇa–bhāvanā, where Anathi Muni explains to King Shrenik that: - No relatives, wealth, doctors, or power can truly protect one from suffering, - Real shelter (nāth) is only in Jin–dharma and self-effort. - Many modern Jain story books and pravachan collections narrate this same incident in slightly different wording but with the same core lesson.

1. Online JainKnowledge reference

A simple written form of this very story (King Shrenik meeting Anathi Muni in the Mandikuli garden, discussion on who is really “anāth” and who is truly protected) is also given here: You can read it here

So, in summary:

• It is an authentic Jain dharma-story,
• Used to illustrate Āśharaṇa–bhāvanā,
• Preserved mainly in later Jain narrative / bhāvanā literature, not as a full episode in the basic Āgams themselves.