Vita tripartita Sancti Patricii

The Vita tripartita Sancti Patricii (English: The Tripartite Life of Saint Patrick) is a bilingual Life of Patrick, written partly in Irish and in parts in Latin from the late 9th century. It is the earliest example of a saint's Life written in the Irish language and it was meant to be read in three parts over the three days of the saint's festival.

...
Wikipedia