oil of saints; manna oil of saints
An oily substance which is said to have flowed, or still flows, from the relics or burial places of certain saints.
Sometimes, the oil in lamps that burn before their shrines, the water that flows from the wells near their burial places, or the oil and water which in some way have come in contact with their relics.
These oils are or have been used by the faithful, with the belief that they will cure bodily and spiritual ailments through the intercession of the saints with whom the oils have some connection.
At present the most famous of these oils is the Oil of Saint Walburga, mentioned as early as the 9th century.
It flows from the stone slab and the surrounding metal plate on which rest the saint's relics in her church in Eichstadt, Bavaria.
A chemical analysis has shown that the fluid is water, but since it came into contact with the relics of the saint, the fact justifies the practise of using it as a remedy for diseases of body and soul.
Among other famous oils are the Oil of Saint Menas, from a holy well near the saint's shrine in the Libyan desert, and the Oil of Saint Nicholas of Myra, which emanates from his relics at Bari, Italy, whither they were brought in 1087.
New Catholic Dictionary