penitential
adjective formal uk/ˌpen.ɪˈten.ʃəl/ us/ˌpen.ɪˈten.ʃəl/
悔罪的，悔过的，忏悔的
showing that you are sorry, especially in a formal religious way, for wrong things that you have done
It was the end of the penitential month of Ramadan. 斋月也是忏悔月到这里就结束了。
a penitential prayer 忏悔的祷告