You're so unfair, sipping from your cup 'til it runneth over, Holy Grail
This line references the biblical phrase my cup runneth over from Psalm 23:5. Jay-Z has himself used this biblical line previously. The phrase can indicate either extreme generosity and copious fortune and wealth, but it is also often expressed sarcastically.
The Holy Grail is the cup from which Jesus drank at the Last Supper. In medieval legends about King Arthur and his Knights of the Round Table — look some of them up, some of them are pretty exciting! — the Grail is constantly chased and pursued: finding the Grail is a life goal. It represents spiritual fulfilment, but it is also made of gold in many interpretations, denoting material wealth. The parallels between the American Dream and the Grail are numerous.
As an idiom, referring to something as the holy grail of [whatever] means it is the thing most sought after.
Not the first time that Jay-Z’s cup overfloweth:
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