O Oriens the ‘O’ Antiphon for December 21st with it’s plea to Christ to "Come and enlighten those who dwell in darkness and the shadow of death" is very closely based on Isaiah 9:2:
Isaiah 9:2: Populus qui ambulabat in tenebris, vidit lucem magnam; habitantibus in regione umbræ mortis, lux orta est eis. (The people that walked in darkness, have seen a great light: to them that dwelt in the region of the shadow of death, light is risen).
Medieval clergy were well aware that the date on which this antiphon was sung was the shortest and darkest of the year and the days would now start to get longer and brighter and conflated this with the idea of Christ’s light abolishing the darkness of sin and of death. The antiphon is sung below by Peter Morton (tenor) and the Choir of St John’s College Choir, Cambridge, conducted by David Hill.