GIT + How to change or remove Passpharse for a GIT SSH Key

>> ssh-keygen -f ~/.ssh/id_rsa -p
 
>> Enter old passphrase: 
>> Key has comment '/home/gsekhar/.ssh/id_castlighthealth_rsa'>>   
Enter new passphrase (empty for no passphrase): >>  
Enter same passphrase again: >> Your identification has been saved with the 
new passphrase.