The prayer of Jacob is located on a Greek magical papyrus. It may plausibly be dated to the first century C.E. but a precise date can not be determined (Horst and Newman: 218). This brings up the issue of magic in the formation of Christ-movement identity. Jerome Neyrey has done a nice analysis of magic from the approach of cultural anthropology (see 'Bewitched in Galatia: Paul and Cultural Anthropology' CBQ 50 (2001): 72-100. William Simmons notes the following concerning magic from the Greek magical papyri.
1. complicated rituals, spells, and recipes;
2. sequential uttering of divine names and nonsense syllables in the hope of hitting the right "password";
3. an eclectic, syncretistic approach;
4. coercion and manipulation of the deities;
5. requests concerning the immediate desires of the individual (2008: 191).
Magic was the lens through which much of the world was understood. Marcel Simon notes concerning Jewish magic had "a great respect for Hebrew phrases which were obviously not understood, but which seemed to the Jews to have magical power; second, a sense of the power of the divine name, and idea certainly not original with Judaism; third, an overwhelming regard for angels and demons, which went over into a clear and elaborate angelolatry" (cited in Newman 2008: 219-20). Judith H. Newman notes "the prayer of Jacob contains the first two elements: arcane and mysterious "Hebraic words and a sense of the power of the divine name and its epithets" (2008: 220).
So, what does this have to do with identity formation? Often we only think through the official institutionalized descriptions of religious practice but we should ask how the broader Roman religious setting and practices formed Christ-movement identity. Magic and the private practice of religion in the Roman empire contributed to the formation of Christ-movement identity in ways other rituals and discourses that are 'approved' by the leaders of the Christ-movement.
So, where would you go to find resources for private religious practices in the first century? Check Galatians 3:1 and then the book of Acts.
Horst, Pieter Willem van der, and Judith H. Newman. Early Jewish Prayers in Greek. Berlin: Walter de Gruyter, 2008.
Simmons, William A. Peoples of the New Testament World: An Illustrated Guide. Peabody, Mass: Hendrickson Publishers, Inc, 2008.