It is said that when a man desires to quit his body he dresses in saffron garments. Therefore it appears that Sati changed her dress, indicating that she was going to quit the body given her by Daksa
SB Canto 4
Maitreya the sage told Vidura: O annihilator of enemies, while thus speaking to her father in the arena of sacrifice, Satī sat down on the ground and faced north. Dressed in saffron garments, she sanctified herself with water and closed her eyes to absorb herself in the process of mystic yoga.
It is said that when a man desires to quit his body he dresses in saffron garments. Therefore it appears that Satī changed her dress, indicating that she was going to quit the body given her by Dakṣa. Dakṣa was Satī's father, so instead of killing Dakṣa she decided that it would be better to destroy the part of his body which was hers. Thus she decided to give up the body of Dakṣa by the yogic process. Satī was the wife of Lord Śiva, who is known as Yogeśvara, the best among all yogīs, because he knows all the mystic processes of yoga, so it appeared that Satī also knew them. Either she learned yoga from her husband or she was enlightened because she was the daughter of such a great king as Dakṣa. The perfection of yoga is that one can give up one's body or release oneself from the embodiment of material elements according to one's desire. Yogīs who have attained perfection are not subject to death by natural laws; such perfect yogīs can leave the body whenever they desire. Generally the yogī first of all becomes mature in controlling the air passing within the body, thus bringing the soul to the top of the brain. Then when the body bursts into flames, the yogī can go anywhere he likes. This yoga system recognizes the soul, and thus it is distinct from the so-called yoga process for controlling the cells of the body, which has been discovered in the modern age. The real yoga process accepts the transmigration of the soul from one planet to another or one body to another; and it appears from this incident that Satī wanted to transfer her soul to another body or sphere.