Farrer interprets John as a rabbinic preacher seeking “new inspiration by drawing old texts into fresh combinations” (p. 30) and thinks that OT was authoritative for John. If the meaning of words and images cannot be found in Revelation, they must be found in the OT.
“Another of St. John’s formal procedures is the exegetical. His whole apocalypse is a visualized meditation on sacred texts” (p. 57).
Caird was heavily influenced by the work of Farrer.
See also Farrer, Rebirth of Images.