 He was ordained a priest in 1982.Arap Korir was consecrated as bishop of the Diocese of Eldoret, Kenya on 2 June 1990 and served there until his death on 30 October 2017.Bishop Korir presided over the church at a time of many turbulent times in the North Rift during the 1992, 1997,2007/08 Kenyan post-election violence, and he played a major role in peace-building and uniting the communities living in this area.