The first day of the week. Jewish converts to Christianity continued to observe the seventh day as the sabbath as well as the first day in commemoration of the Resurrection and Pentecost. But, as Jewish influence waned with the spread of the Church, Sunday became the holy day. Paul's influence was strong in this change (I Corinthians 16:1-2). The name "Lord's Day" appeared first in Revelation (Revelation 1:10).