I think it is still normally used, meaning, in this case, that Hassan has become mature or legally of age (e.g. 18 years old).
I think most people would take this meaning, but it is more common to use "come of age" to represent the varying ages at which legal, physical or mental maturity is reached. There is also the common use "she is of an age......" which can be used in two situations:-
She is of an age where sexual morality was stricter. Namely she is old enough to know a time when things were different.
She is of an age where/when she does not worry about problems which cannot be solved. Namely she has reached a fairly high level of maturity through age. Many people use "at an age" in this example.