Library Pseudo-Clement Clementine Homilies
Homily 18, Chapter 20: Some Parts of the Old Testament Written to Try Us
But one might with good reason maintain that it was with reference to those who thought Him to be such that the statement was made, 'No one knows the Father but the Son, as no one knows even the Son, but the Father.' And reasonably. For if they had known, they would not have sinned, by trusting to the books written against God, really for the purpose of trying. But somewhere also He says, wishing to exhibit the cause of their error more distinctly to them, 'On this account ye do err, not knowing the true things of the Scriptures, on which account you are ignorant also of the power of God.' Wherefore every man who wishes to be saved must become, as the Teacher said, a judge of the books written to try us. For thus He spoke: 'Become experienced bankers.' Now the need of bankers arises from the circumstance that the spurious is mixed up with the genuine.
English translation in Ante-Nicene Fathers, Vol. VIII (eds. Alexander Roberts and James Donaldson; Buffalo: Christian Literature Publishing Co., 1886). Public domain. Digital text via New Advent Church Fathers.