Augustine of Hippo

(Tr. xliii. 15) Some heretics say that the God proclaimed in the Old Testament is not the Father of Christ, but a kind of prince of bad angels. These He contradicts when He calls Him His Father, whom the Jews called their God, and knew not. For had they known Him, they would have received His Son. Of Himself however He adds, But I know Him. And here too, to men judging after the flesh, He might appear arrogant. But let not arrogance be so guarded against, as that truth be deserted. Therefore our Lord says, And if I should say I know Him not, I should be a liar like unto you.