Prime is the rare liturgical institution whose founding anecdote survives. John Cassian, writing in the 420s for the monasteries of Gaul about the customs of the East, reports that in the monastery at Bethlehem the brothers, having finished the night office and Lauds, would return to bed until the third hour, and that some abused the interval into serious sleep; to close the loophole a new morning service was instituted at the first hour, and, he says, the custom spread. Liturgical historians accept the substance: Prime is a monastic invention of the late fourth century, younger than the hours around it and born of discipline rather than symbolism. Its content stayed suitably practical.
The hour's psalms were brief; its collect, memorably rendered in the Anglican tradition as the prayer that we fall into no sin, neither run into any kind of danger, asked simply for a safe day; and in the medieval West a second section followed in the chapter house: the reading of the martyrology announcing the saints of the coming day, the necrology remembering the dead, the assignment of the day's work, and the abbot's blessing. Prime was thus the join between prayer and labour, the office that dispatched the community into its duties, and its rhythm shaped institutional life far beyond the cloister, giving cathedral schools and colleges their morning order. Its practicality was also its vulnerability: an hour instituted for monks with a gap in their morning made less sense for clergy whose Lauds already met the sunrise.