SB 1.13.58

dahyamāne ’gnibhir dehe
 patyuḥ patnī sahoṭaje
bahiḥ sthitā patiṁ sādhvī
 tam agnim anu vekṣyati
Synonyms: 
dahyamāne — while it is burning; agnibhiḥ — by the fire; dehe — the body; patyuḥ — of the husband; patnī — the wife; saha-uṭaje — along with the thatched cottage; bahiḥ — outside; sthitā — situated; patim — unto the husband; sādhvī — the chaste lady; tam — that; agnim — fire; anu vekṣyati — looking with great attention will enter the fire.
Translation: 
While outside observing her husband, who will burn in the fire of mystic power along with his thatched cottage, his chaste wife will enter the fire with rapt attention.
Purport: 

Gāndhārī was an ideal chaste lady, a life companion of her husband, and therefore when she saw her husband burning in the fire of mystic yoga along with his cottage of leaves, she despaired. She left home after losing her one hundred sons, and in the forest she saw that her most beloved husband was also burning. Now she actually felt alone, and therefore she entered the fire of her husband and followed her husband to death. This entering of a chaste lady into the fire of her dead husband is called the satī rite, and the action is considered to be most perfect for a woman. In a later age, this satī rite became an obnoxious criminal affair because the ceremony was forced upon even an unwilling woman. In this fallen age it is not possible for any lady to follow the satī rite as chastely as it was done by Gāndhārī and others in past ages. A chaste wife like Gāndhārī would feel the separation of her husband to be more burning than actual fire. Such a lady can observe the satī rite voluntarily, and there is no criminal force by anyone. When the rite became a formality only and force was applied upon a lady to follow the principle, actually it became criminal, and therefore the ceremony was to be stopped by state law. This prophecy of Nārada Muni to Mahārāja Yudhiṣṭhira forbade him to go to his widowed aunt.