Make sure 'ssh copy enable/ssh scopy enable' is on, and that ssh for that ip/subnet is enabled.
then scp from one ASA to the other
ASA# copy /noconfirm asa917-12-smp-k8.bin scp://username:password@IP_Addr/asa917-12-smp-k8.bin
I don't like having to put the password in clear text on the command line, but it doesn't seem to prompt interactively for a password. (even if I don't use /noconfirm)
please do not forget to rate.