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