Because of her chastity, the woman was very powerful. Therefore when she heard about the curse (Markandeya Rsi, who cursed her husband to die at sunrise) , she vowed to stop the sunrise
“The wife of a brāhmaṇa suffering from leprosy manifested herself as the topmost of all chaste women by serving a prostitute to satisfy her husband. She thus stopped the movement of the sun, brought her dead husband back to life and satisfied the three principal demigods (Brahmā, Viṣṇu and Maheśvara).
The Āditya Purāṇa, Mārkaṇḍeya Purāṇa and Padma Purāṇa tell about a brāhmaṇa who was suffering from leprosy but had a very chaste and faithful wife. He desired to enjoy the company of a prostitute, and therefore his wife went to her and became her maidservant, just to draw her attention for his service. When the prostitute agreed to associate with him, the wife brought her the leprotic husband. When that leper, the sinful son of a brāhmaṇa, saw the chastity of his wife, he finally abandoned his sinful intentions. While coming home, however, he touched the body of Mārkaṇḍeya Ṛṣi, who thus cursed him to die at sunrise. Because of her chastity, the woman was very powerful. Therefore when she heard about the curse, she vowed to stop the sunrise. Because of her strong determination to serve her husband, the three deities—namely Brahmā, Viṣṇu and Maheśvara—were very happy, and they gave her the benediction that her husband would be cured and brought back to life. This example is given herein to emphasize that a devotee should engage himself exclusively for the satisfaction of Kṛṣṇa, without personal motives. That will make his life successful.