The moment
By the Sri Lankan chronicles, Ashoka's son Mahinda converted King Devānampiya Tissa, who gave the monks the Mahāmegha park at Anurādhapura, and Ashoka's daughter Saṅghamittā brought a cutting of the Bodhi tree. The Mahāvihāra founded there became the ancestor of the lineage later called Theravāda.
People: Mahinda, Saṅghamittā, Devānampiya Tissa