brew install sshpass
Installing sshpass from Homebrew? Be prepared for this:
$ brew install sshpass ==> Error: No available formula with the name "sshpass" ==> We won't add sshpass because it makes it too easy for ==> novice SSH users to ruin SSH's security.
The (security) needs of many outweigh the needs of the few. Normally I find such overbearing policy frustrating, but in this case: good call.