Emil Schürer writes:
“The third chief group of Philo’s works on the Pentateuch is a Delineation of the Mosaic Legislation for non-Jews. In this whole group indeed, the allegorical explanation is still occasionally employed. In the main however we have here actual historical delineations, a systematic statement of the great legislative work of Moses, the contents, excellence and importance of which, the author desires to make evident to non-Jewish readers, and indeed to as large a circle of them as possible. For the delineation is more a popular one, while the large allegorical commentary is an esoteric, and according to Philo’s notions a strictly scientific work. The contents of the several compositions forming this group differ indeed considerably, and are apparently independent of each other. Their connection however, and consequently the composition of the whole work, cannot, according to Philo’s own intimations, be doubtful. As to plan it is divided into three parts. (a) The beginning and as it were the introduction to the whole is formed by a description of the creation of the world (κοσμοποιια), which is placed first by Moses for the purpose of showing, that his legislation and its precepts are in conformity with the will of nature (προς το βουλημα της φυσεως), and that consequently he who obeys it is truly a citizen of the world (κοσμοπολιτης) (de mundi opif. § 1). This introduction is followed by (b) biographies of virtuous men. These are, as it were, the living, unwritten laws (εμψυχοι και λογικοι νομοι de Abrahamo, § 1, νομοι αγραφοι de decalogo, § 1), which represent, in distinction from the written and specific commands, universl moral norms (τους καθολικωτερους και ωσαν αρχετυπους νομους de Abrahamo, § 1). Lastly, the third part embraces (c) the delineation of the legislation proper, which is divided into two parts: (1) that of the ten chief commandments of the law, and (2) that of the special laws belonging to each of these ten commandments. Then follow by way of appendix a few treatises on certain cardinal virtues, and on the rewards of the good and the punishment of the wicked. This survey of the contents shows at once, that it was Philo’s intention to place before his readers a clear description of the entire contents of the Pentateuch, which should be in essential matters complete. His view however is in this respect the genuinely Jewish one, that these entire contents fall under the notion of the νομος.” (The Literature of the Jewish People in the Time of Jesus, pp. 338-339

Emil Schürer comments:
“Βιος σοφου του κατα διδασκαλιαν τελειωθεντος η περι τομων αγραφων [α], ο εστι περι Αβρααμ. De Abrahamo (Mangey, ii. 1-40).—With this composition commences the group of the νομοι αγραφοι, i.e. the βιοι σοφων (de decalogo, § 1), the biographies of virtuous men, who exhibit by their exemplary behaviour the universal types of morality. Of such types there are twice three, viz. (1) Enos, Enoch, Noah; (2) Abraham, Isaac, Jacob. Enos represents ελπις, Enoch μετανοια και βελτιωσις, Noah δικαιοσυνη (de Abrahamo, § 2, 3, 5). The second triad is more exalted: Abraham is the symbol of διδασκαλικη αρετη (virtue acquired by learning), Isaac of φυσικη αρετη (innate virtue), Jacob of ασκητικη αρετη (virtue attaiend by practice), see de Abrahamo, § 11; de Josepho, § 1 (Zeller, iii. 2. 411). The first three are only briefly dwelt on. The greater part of this composition is occupied with Abraham.—In Eusebius, H. E. ii. 18. 4, the title runs: βιου [read βιος] σοφου του κατα δικαιοσυνην τελειωθεντος η [περι] νομων αργαφων. Δικαιοσυνην, instead of the διδασκαλιαν furnished by the Philo manuscripts, is here certainly incorrect. For Abraham is the type of διδασκαλικη αρετη. The number α must be inserted after αργαφων, this book being only the first of the unwritten laws.” (The Literature of the Jewish People in the Time of Jesus, p. 341)

F. H. Colson writes (Philo, vol. 6, pp. 2-3):

After stating his intention to follow Moses in describing the “living” before proceeding to the written Laws (1-6) Philo deals with the first and less perfect triad. First Enos the hoper, whose name equivalent to “Man” shows that hope is the first mark of a true man (7-10). Secondly repentance represented by Enoch, who was “transferred” i.e. to a better life and was “not found,” for the good are rare and solitary (17-26). Thirdly, Noah, who was “just” in comparison with the wicked generation destroyed by the Flood (27-46).

The higher triad of the three great Patriarchs are not only typical of the trinity, Teaching, Nature and Practice, but are also the parents of Israel, the soul which attains to the sight of God (48-59). To come to Abraham himself, the literal story of his migrations shows his self-sacrifice (60-67); allegorically it denotes the soul’s journey from godless astronomy first to self-knowledge (Haran), then to the knowledge of God (68-88). His adventures in Egypt (89-98) suggest that the tortures which plagued Pharaoh represent what the sensual mind suffers from the virtues which, while it professes to love them, are incompatible with it (99-106). Next comes the story of the three Angelic Visitors (107-118). Allegorically they represent the Self-existent and the beneficent and sovereign potencies apprehended according as the soul can rise to the full conception or is moved by hope of benefits or fear, and Philo points out that while men distrust these last motives, God does not hold them worthless (119-132). In fact the tale of the destruction of the Cities of the Plain represents the Self-existent as leaving these tasks to His subordinates (133-146). This leads him to an allegory in which the five cities are the five senses, the noblest of which, sight, is figured by Zoar (147-166).

Next comes the sacrifice of Isaac (167-177). The greatness of Abraham is vindicated against hostile criticisms based on the frequency of similar stories of child immolation (178-199). Allegorically the story means that a devout soul often feels a duty of surrendering its “Isaac,” Joy, which nevertheless through God’s mercy it is allowed to retain (200-207).

These narratives have illustrated Abraham’s piety. Next comes his kindness to men as shewn in his settlement of the dispute with Lot (208-216). This dispute may be taken to represent allegorically the incompatibility of love for the goods of the soul with love for bodily or external things (217-224). Then his courage appears in his victory over the four kings who had routed the armies of the five cities (225-235), and this conflict is allegorized as one between the four passions and the five senses, in which the intervention of reason turns the scale against the former (236-244). Philo now goes on to say something of the virtues of Sarah, particularly as shewn by her advocacy of the mating with Hagar (245-254) and this leads on to an account of the grief coupled with resignation shown by Abraham at her death (255-261). The treatise concludes with an eloquent praise of Abraham’s faith and of his right to the title of “Elder” and the crowning tribute that he both did the law and was himself the Law (262-end).