Checkout the latest glibc in development:
git clone https://sourceware.org/git/glibc.git
cd glibc
git checkout master
Releases are available by source branch checkout (gitweb) and tarball via ftp.
Checkout the latest glibc 2.40 stable release:
git clone https://sourceware.org/git/glibc.git
cd glibc
git checkout release/2.40/master
Release tarballs are available via anonymous ftp at https://ftp.gnu.org/gnu/glibc/ and its mirrors.