In the closing days of Advent, the feast of Saint Thomas

... the Church recommends [this feast] to our meditation at this season, as a fit preparative to our Lord’s Nativity. For unless we believe with St. Thomas, that the same Jesus, whose birth we immediately after commemorate, is the very Christ, “our Lord and our God,” neither his birth, death, nor resurrection will avail us any thing.

Richard Mant Biographical Notices of the Apostles, Evangelists, and Other Saints: With Reflexions and Collects; Adapted to the Minor Festivals of the United Church of England and Ireland (1828).