How to remove passphrase from a private key

Sometimes, I feel to remove the passphrase from a key file.

$ ssh-keygen -p -f /the/path/of/a/key
Enter old passphrase
Enter new passphrase - Enter
Confirm new passphrase - Enter

Then, it makes me easy…

Reference:

https://stackoverflow.com/questions/112396/how-do-i-remove-the-passphrase-for-the-ssh-key-without-having-to-create-a-new-ke