And there appeared unto them Elijah with Moses: and they were talking with Jesus.
All Commentaries on Mark 9:4 Go To Mark 9
Tertullian of Carthage
AD 220
Since, therefore, He reserves to some future time His presence and speech face to face with Moses-a promise which was afterwards fulfilled in the retirement of the mount (of transfiguration), when as we read in the Gospel "Moses appeared talking with Jesus"