RE-MARRIAGE. Re-marriage may take place with the divorcer before or after the completion of the ‘iddah, provided only the first or second sentence of divorce has been pronounced, but it cannot take place after a three-fold divorce until the divorced wife is married to another man and is divorced by him after the second marriage has been consummated. This is both Sunni and Shi’ah law (Tagore Law Lectures.)
A widow can marry again at the expiration of four months and ten days after the death of her former husband. There is no restriction as to the period for a widower.
Based on Hughes, Dictionary of Islam