With an outstretched arm: this is the sword, as it is written, “And a drawn sword in His hand stretched out over Jerusalem”: What made the first born of Egypt worthy of being killed the Holy One and not by one of God's heavenly destroyers? Rather, it must be that they were killed by God's sword and not by the Holy One Himself. The Bible says, “David looked up and saw the angel of the Lord standing between heaven and earth, with a drawn sword in His hand directed against Jerusalem.” (I Chronicles 21:16) If they died at the hands of an angel all the more so did the Egyptians!