Negative Mitzvah 357: It is forbidden to marry a childless widow before she receives permission from her brother-in-law
Deuteronomy 25:5 "The wife of the dead man shall not marry an outsider"

If a woman's husband passes away and they had no children it is a Mitzvah for the brother of the dead husband to marry her (see Positive Mitzvah 216).

Since it is his opportunity to continue the family name of his dead brother, no one else is permitted to take the widow as a wife.

If he does not wish to marry her and fulfills the proper ceremony of "Chalitzah" (see Positive Mitzvah 217), the woman is free to marry someone else.

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You can read about G-d's involvement in this world in a book of philosophy. Or you can see it in real life in your business. Look carefully, objectively, and you will realize that for you to make a living there must occur constant miracles, each greater than the miracle of the splitting of the Red Sea. The fact that you don't notice these miracles doesn't make them any less miracles. On the contrary, their loftiness transcends your perception.

From: "Bringing Heaven Down to Earth" by Tzvi Freeman - tzvif@aol.com members.aol.com/tzviF