Kathina is the robe-offering ceremony that closes the three-month rains retreat (vassa), and it is the largest lay merit-making occasion of the Theravada Buddhist year. During the monsoon, monks remain settled in one monastery rather than travelling; at the end of the retreat, in the month that follows (roughly October-November), the lay community presents cloth for robes to the resident community of monks as a whole, rather than to any individual, and the monks themselves decide, according to the discipline, who is to receive and make it up. The offering follows the ancient allowance recorded in the monastic code (Vinaya), where the Buddha is said to have permitted the Kathina robe to monks who had kept the full retreat.
Several features make the occasion weighty. A monastery may hold the ceremony only once a year, and only if a sufficient number of monks kept the full retreat there, so that an invitation to sponsor a Kathina is a matter of some standing in the community; the merit is regarded as especially great. In Thailand, Myanmar, Sri Lanka, Laos and Cambodia the day is marked by processions, music, and the offering of a great deal besides cloth, robes, alms and support for the monastery, and it is often a whole village or a wider network of donors that mounts it. Where the older discipline is kept strictly, the cloth is cut, sewn and dyed within the same day, a demanding collective labour that itself expresses the devotion of the offering. Kathina thus renews the material support of the Sangha at the turning of the monastic year and binds the lay and monastic communities in a shared act of giving.