Which preposition to use with expounder

of Occurrences 52%

Take him altogether he was our biggest gun, and it's a pity he went off as he did, for he was the Great Expounder of the Constitution.

in Occurrences 2%

It entered even into the Christian schools, especially at Alexandria; it has ever assisted and animated the earnest searchers after the certitudes of life; it has permeated the intellectual world, and found admirers and expounders in all the universities of Europe and America.

than Occurrences 1%

Who, in this respect, made him a greater light and a clearer expounder than the Christian Paley?

Which preposition to use with  expounder