Who is Ravenhill quoting...?

"The prophet, by the very nature of his calling is a tragic figure. He has a fierce loyalty to God, and a burning heart of compassion for a lost world."Ravenhill has quoted this more than once in his sermons. Does anyone know who the 'famous Jewish scholar' is?

It may be Abraham Joshua Heschel, from his book "The Prophets". It has many statements like that.