John Chrysostom : "And he gave him the covenant of circumcision: and so he begat Isaac." Here he lets himself down to lower matters. "And circumcised him on the eighth day: and Isaac begat Jacob, and Jacob the twelve patriarchs." Here he seems to hint now at the type. And observe, how, while he seems to concede something to circumcision, he in fact allows it nothing; since the Promise was before it, and it followed after. — Homily on Acts 16