The Apostolic Fathers
These were early Christian writers and theologians who lived in the 1st and 2nd centuries AD. They are believed to have known some of the Twelve Apostles or to have been significantly influenced by them. Their writings, which include letters and other texts, serve as a crucial link between the New Testament and the organized Christian communities that followed. These writings provide insight into the beliefs and practices of early Christianity and are still studied today for their theological significance.
https://en.wikipedia.org/wiki/
https://www.catholic.org/saints/
https://missions.ewtn.com/seasonsandfeastdays/stssimonandjude
https://en.wikipedia.org/wiki/Apostolic_Fathers#List_of_works