rsync --partial --progress --rsh=ssh user@ip:remotepath localpath

Breakdown:

--partial – this lets rsync know that it should keep the already downloaded partial files and download only the remainder
--progress – show the progress of the transfer
--rsh=ssh – use the ssh protocol
user@ip – remote machine. This might be the alias you’ve given it in your ssh config file.
remotepath – path to the file in the remote machine
localpath – path to the partially-downloaded local file