The blessing of wine on the Feast of St. John comes from a Catholic legend that St. John was given a chalice of poisoned wine as a test by the pagan high priest of the Temple of Diana in Ephesus. When St. John blessed the chalice, the poison escaped in the form of a small dragon. St. John was then able to drink the wine from the chalice without harm.
This first written citation of the legend was by Jacobus de Voragine in the 13th century and the scene was captured in a number of paintings, notably one (shown below) by El Greco in 1600.
The tradition is for the wine to be blest on the Feast of St. John. Then, before dinner on the feast day, a toast is offered for St. John using the wine. The host lifts his glass to each of his guests individually and says, “I drink you the love of St. John.” The response is, “I thank you for the love of St. John.”
The blessing of the wine will be after the 9:00 A.M. Mass on December 27.