ויקרא פרק כו, כ וְתַם לָרִ יק כ ֹּחֲכֶם
מדרש רבה זה המשיא את בתו ונותן לה ממון הרבה ולא הספיקו שבעת ימי משתה לצאת עד שמתה בתו, נמצא קובר את בתו ומאבד את ממונו
In general, a husband becomes the owner of the wedding gifts after the wedding. Thus, in event of a death of the daughter immediately after the wedding, the father stands to lose his daughter and the money of the gifts for the wedding (נדוניא). Tosefos does honor the written request of the father that writes that the gifts to his daughter do not transfer to the son-in-law, if the daughter was to die soon after the wedding. The intent of the father is that the gifts to his daughter are for her benefit and not someone else.
Most recognize the concept that the husband inherits the wife is a rabbinical decree. Therefore, based on this Medrosh, Rabbenu Tam and the Rabbis of France issued a decree that if a wife was to die during the first year after the wedding, then the all the bride’s personal property would revert to her father or her legal heirs (not to the spouse). In the lands of Poland and the East, they decreed that if the wife was to die during the first three years of marriage, all her personal property would go to her heirs (and not the spouse). And if this occurred in the fourth and fifth years after the wedding, then the husband and her heirs would split the property 50-50.
