4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the hash code to index the “empty tree” (before your first commit) in git version control system.

It is useful if you want to export a patch actually contains everything:

git format-patch 4b825dc642cb6eb9a060e54bf8d69288fbee4904 --stdout > allinone.patch

Credits

• How to get Git diff of the first commit? - Thank CB Bailey for the answer.