1,584. From What a Kesubah May and May Not Be Collected
Hilchos Ishus 16:4
The Sages also decreed that when a woman comes to collect the value of her kesubah after her husband's death, she must first take an oath while holding something holy to the effect that her husband didn’t leave any property with her, that she didn’t sell him the rights to her kesubah and that she hasn’t waived payment. Her wardrobe is appraised and deducted from the value of her kesubah. However, if a husband voluntarily divorces his wife, then she can collect the value of her kesubah without an oath and the value of her wardrobe is not deducted. The reason is because the husband bought the clothes for his wife and in this case he’s the one who wants a divorce, not her.
Hilchos Ishus 16:5
The Sages also ruled that a widow only collects the value of her kesubah from real estate. She does not collect from any increase in that property’s value after the husband’s death. Similarly, after their father dies, daughters do not receive their maintenance from the posthumous increase in the value of his property. A woman likewise does not collect the value of her kesubah from the increase in value of real estate that was brought about by a buyer. This is so even though other creditors can collect from this improvement. These rules are leniencies regarding the payment of a kesubah.