The transverberation is a mystical grace wherein the Saint’s heart was pierced with a “dart of love” by an angel. St. John of the Cross, “It will happen that while the soul is inflamed with the Love of God, it will feel that a seraph is assailing it by means of an arrow or dart which is all afire with love. And the seraph pierces and in an instant cauterizes this soul, which, like a red-hot coal, or better a flame, is already enkindled. The soul is converted into an immense fire of Love. Few persons have reached these heights.” - Source
ON THE PURIFICATION OF LOVE
After ecstatic union, as a preparation for the transforming union, there is a very painful purification of love, of which St. Teresa speaks at the end of the sixth mansion. The saint says:
The heart receives, it knows not how or whence, a blow as from a fiery dart. . . in the very depths and center of the soul. . . . This resembles the pains of purgatory. . . . The spiritual torments are so much more keen that the bodily ones remain unnoticed. . . . She feels a strange loneliness, finding no companionship in any earthly creature. . . . Meanwhile all society is a torture to her. She is like one suspended in mid-air, who can neither touch the earth nor mount to heaven; she is unable to reach the water while parched with thirst and this is not a thirst that can be borne, but one which nothing will quench. . . . Though this torment and grief could not, I think, be surpassed by any earthly cross. . . , yet they appeared to her as nothing in comparison with their recompense. The soul realizes that it has not merited anguish which is of such measureless value.(24)
In the same chapter of the sixth mansion, the saint goes on to say: "This agony does not continue for long in its full violence - never, I believe, longer than three or four hours; were it prolonged, the weakness of our nature could not endure it except by a miracle. . . . This favor entails great suffering but leaves most precious graces within the soul, which loses all fear of any crosses it may henceforth meet with, for in comparison with the acute anguish it has gone through, all else seems nothing. . . . It is also much more detached from creatures, having learned that no one but its Creator can bring it consolation and strength." - Garrigou Lagrange