Widows had their head shaved and forced into seclusion in South. Why??
Because it is forbidden in scripture.
This chapter of the Manu Smriti says that a widow cannot remarry, except for her brother-in-law under certain circumstances.
By twice-born men a widow must not be appointed to (cohabit with) any other (than her husband); for they who appoint (her) to another (man), will violate the eternal law.
In the sacred texts which refer to marriage the appointment (of widows) is nowhere mentioned, nor is the re-marriage of widows prescribed in the rules concerning marriage.
This practice which is reprehended by the learned of the twice-born castes as fit for cattle is said (to have occurred) even among men, while Vena ruled.
That chief of royal sages who formerly possessed the whole world, caused a confusion of the castes (varna), his intellect being destroyed by lust.
Since that (time) the virtuous censure that (man) who in his folly appoints a woman, whose husband died, to (bear) children (to another man).
If the (future) husband of a maiden dies after troth verbally plighted, her brother-in-law shall wed her according to the following rule.
Having, according to the rule, espoused her (who must be) clad in white garments and be intent on purity, he shall approach her once in each proper season until issue (be had).
This chapter of the Adi Parva of the Mahabharata says the same thing:
Be the husband dead or alive, it shall not be lawful for a woman to have connection with another.
By the way, there is one exception to the rule, namely that if her first marriage has not been consummated then a widow can marry again. See this chapter of the Vasishta Dharma Sutras:
- 'If a damsel at the death of her husband had been merely wedded by (the recitation of) sacred texts, and if the marriage had not been consummated, she may be married again.'
This chapter of the Anushasana Parva of the Mahabharata
Some say that the virgin wife or widow,--one, that is, whose marriage has not been consummated with her husband by actual sexual congress in consequence of his absence or death,--may be allowed to unite herself with her husband's younger brother or such other relation. The husband dying before such consummation, the virgin-widow may either surrender herself to her husband's younger brother or betake herself to the practice of penances
By the way, I should note that this verse from the Brahma Vaivarta Purana says that a widow marrying her brother-in-law is no longer allowed in the Kali Yuga:
In this Age of Kali, five acts are forbidden: the offering of a horse in sacrifice, the offering of a cow in sacrifice, the acceptance of the order of sannyāsa, the offering of oblations of flesh to the forefathers, and a man’s begetting children in his brother’s wife.
But like many verses of the Brahma Vaivarta Purana, this verse is considered by many to be an interpolation.