Be not grieved; tests lead to the development of holy souls and the ardor of the flame of fire causeth the pure gold to shine and the violence of winds is conducive to the growth and thriving of a firm and well rooted tree.
(‘Abdu’l-Bahá, Tablets of ‘Abdu’l-Bahá v2, p. 297)
Unless the season of winter appear, thunder roll, lightning flash, snow and rain fall, hail and frost descend and the intensity of cold execute its command, the season of the soul-refreshing spring would not come, the fragrant breeze would not waft, the moderation of temperature would not be realized, the roses and hyacinths would not grow, the surface of the earth would not become a delectable paradise, the trees would not bloom, neither would they bring forth fruits and leaves. That fierce inclemency of cold, snow, frost and tempest was the beginning of the manifestation of these roses, hyacinths, buds, blossoms and fruits.
(‘Abdu’l-Bahá, Tablets of ‘Abdu’l-Bahá v3, p. 655)