Aurelius Prudentius Clemens - Corde Natus ex Parentis

Prudentius was a Roman poet who lived in the province of Hispania in the late fourth and early fifth century.  He blended classical themes with Christian ones, and became enormously influential in the middle ages.  C. S. Lewis thought him over rated but there is no doubt that he authored the second oldest Christmas Carol.  It is still performed today, 1600 years later.