Christopher is right, tagging will help you do this. I recommend deleting the branch name too to make it a little harder for someone to checkout the branch and make edits.
First, merge the branch into develop
git checkout develop
git merge --no-ff feature_1
Then checkout the branch
git checkout feature_1
Then create a tag, with a comment.
git tag -a -m "Freezing a feature branch that fixes.." feature_1_frozen
Then delete the branch
git checkout develop
git branch -d feature_1
After doing this, you won’t be able to checkout the branch by name. Instead you’ll be able to checkout the tag by name, this will put you into a detached head state which will deter changes to the code.
Now to wrap things up and sync with origin…
Push the update and new tag
git push --tags origin develop
Delete the remote feature branch
git push origin :feature_1