Ibrahim (may Allah have mercy on him) said: When a person makes a bequest of a third or a quarter of his wealth, it will be paid from the specified property and from debts. And if he makes a bequest of fifty, sixty, or up to a hundred (i.e., less than a third), then the bequest will be paid from the specified property until it equals a third (i.e., until it becomes one third).
Hadith Referenceسنن دارمي / من كتاب الوصايا / 3256