When may a widow remarry? Is there any other waiting period?

A widow may remarry as soon as the ʿiddah of death ends, that is after 4 months 10 days, or after giving birth if she is pregnant. There is no additional waiting period in the Shariah. During the ʿiddah, a man may only express interest by hint (taʿridh), not by an explicit proposal, and a contract during the ʿiddah is invalid. After the ʿiddah, a widow who has been married before must give her permission clearly and still needs a wali. Wives of the Prophet ﷺ such as Ummu Salamah and Saudah were widows married after their ʿiddah. In Malaysia, include the previous husband's death certificate when applying for permission to marry at the religious affairs office.