Faustus does not think it would be a great honor to sit down with Abraham, Isaac and Jacob, whose moral characters as set forth in the Old Testament he detests. He justifies his subjective criticism of Scripture. Augustine sums up the argument, claims the victory, and exhorts the Manichæans to abandon their opposition to the Old Testament notwithstanding the difficulties that it presents, and to recognize the authority of the Catholic Church.
Source: Reply to Faustus the Manichaean (New Advent)