What is the legal effect of heirs approving a property endowment (Waqf) made by the testator during his final illness?

Primary text

The endowment made by the testator during his final illness becomes valid if the heirs approve, provided that the approval is ruled to be a pure implementation (tanfidh) of the original act. If the ruling is that the act constitutes a fresh gift, it is not valid, because in doing so, they would effectively be establishing an endowment upon themselves.