The executor valued one-third of the estate at one million, so he ordered it to be paid out, but it was not paid out until the estate increased. What is the ruling?

Question:
He says: Honorable Shaykh, may Allah grant you success. He says: My father looked at one-third of his wealth and found it to be one million riyals, so he instructed us in a document to pay out the one million to build a mosque. He says: Now, after two years have passed, the wealth has increased, and the written amount has not changed. So are we bound by the specified amount? How? He says: My father looked at one-third of his wealth, found it to be one million riyals, and instructed us in a document to pay out one million to build a mosque. Now, after two years have passed, the wealth has increased, and the amount has not changed.

Answer:
Yes, the one million is to be executed, and the increase in the wealth belongs to the heirs. The increase in the estate is for the heirs, and the one million does not change.