This paper will offer some reflections on writing a new translation and commentary on Philo’s De Decalogo, itself the earliest known commentary on the Ten Commandments. Special attention will be given to Philo’s effort to elucidate the reasons for the commandments, and their benefits to the human soul and human society, with particular focus on the Fifth Commandment, situated, as Philo sees it, ‘on the borderline’ between the two sets of five commandments.