sshpass formula for Homebrew.
Homebrew maintainers reject adding sshpass for security reasons, but some users need this.
brew install hudochenkov/sshpass/sshpass
Or brew tap hudochenkov/sshpass and then brew install sshpass.
Or install via URL (which will not receive updates):
brew install https://raw.githubusercontent.com/hudochenkov/homebrew-sshpass/master/sshpass.rb