I was facing the same error on my MacBook Air(macOS BigSur) Laptop while installing the Numpy package via integrated terminal of VS Code. And I found the solution:
So previously I was using older version of pip i.e. 19.2.3.
But when I upgraded it to the latest version using command
pip install --upgrade pip
and after that when running the command
pip install numpy
it worked absolutely fine.
At the time running the above commands, my python version was 3.8.2.