ssh(1) -A gateway-host ssh target-host hostname
OpenSSH SSH client (remote login program)
-A      Enables forwarding of the authentication agent connection.  This can also be specified on a per-
        host basis in a configuration file.

        Agent forwarding should be enabled with caution.  Users with the ability to bypass file permissions
        on the remote host (for the agent's UNIX-domain socket) can access the local agent through the
        forwarded connection.  An attacker cannot obtain key material from the agent, however they can
        perform operations on the keys that enable them to authenticate using the identities loaded into
        the agent.
ssh connects and logs into the specified hostname (with optional user name).  The user must prove his/her
identity to the remote machine using one of several methods depending on the protocol version used (see

If command is specified, it is executed on the remote host instead of a login shell.
source manpages: ssh