nemo est heres viventis

Etymology
Of uncertain specific origin; current as a maxim across Western Europe by the 16th–17th centuries, in both England and the Continent. Later treated as a precept of common law, though its occasional ascription to the 13th-century English jurist is spurious.

Proverb

 * 1) “No one is heir of a living person”: the inheritance of an estate is decided only upon the death of its owner, and nobody is “heir” while that person is alive (only heir apparent or heir presumptive).