scp(1) -i /path/to/key foo.txt username@beluga.computecanada.ca:work/
secure copy (remote file copy program)
-i identity_file
        Selects the file from which the identity (private key) for public key authentication is read.  This
        option is directly passed to ssh(1).
scp [-12346BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file] [-l limit] [-o ssh_option] [-P port]
    [-S program] [[user@]host1:]file1 ... [[user@]host2:]file2
source manpages: scp