Adam Clarke on Genesis 12:17

The Lord plagued Pharaoh - What these plagues were we know not. In the parallel case, Gen 20:18, all the females in the family of Abimelech, who had taken Sarah in nearly the same way, were made barren; possibly this might have been the case here; yet much more seems to be signified by the expression great plagues. Whatever these plagues were, it is evident they were understood by Pharaoh as proofs of the disapprobation of God; and, consequently, even at this time in Egypt there was some knowledge of the primitive and true religion.