Enter passphrase for key '/Users/emai/.ssh/id_rsa':
means that your key is protected by a password entered when that key was generated
every time you use it it will ask for a password.
by running ssh-keygen one more time without entering the password you've generated another key.
No password in the key - no password prompt :)
here is quote from ssh-keygen manpage:
Normally this program generates the key and asks for a file in which to store the private key. The public key is stored in a file
with the same name but ``.pub'' appended. The program also asks for a
passphrase. The passphrase may be empty to indicate no passphrase (host keys must have an empty passphrase), or it may be a
string of arbitrary length. A passphrase is similar to a password,
can be a phrase with a series of words, punctuation, numbers, whitespace, or any string of characters you want. Good passphrases
are 10-30 characters long, are not simple sentences or otherwise
guessable (English prose has only 1-2 bits of entropy per character, and provides very bad passphrases), and contain a mix of
upper and lowercase letters, numbers, and non-alphanumeric characters.
passphrase can be changed later by using the -p option.
There is no way to recover a lost passphrase. If the passphrase is lost or forgotten, a new key must be generated and the
corresponding public key copied to other machines.