On this day we celebrate the feast of St. Luke, Evangelist.
The First Reading at Mass, from Paul to Timothy, begins with this: "Demas, enamored of the present world, deserted me and went to Thessalonica, Crescens to Galatia, and Titus to Dalmatia, Luke is the only one with me."
Demas deserted, but Luke stayed. John Keble, the great poet of the Oxford Movement, compares the two in "St. Luke,"  in The Christian Year,1827.
For modern biblical scholarship on St. Luke, see The Birth of the Messiah: A Commentary on the Infancy Narratives in the Gospels of Matthew and Luke,  by Raymond E. Brown, Yale University Press, updated edition, 1999; and Meeting St. Luke Today: Understanding the Man, His Mission, and His Message,  by Daniel J. Harrington, SJ, Loyola Press, 2009.