[4] The sources for Jacob's biblical citations are composed of a mixture stemming from the Septuagint, the Peshitta, and the Syro-Hexaplar version.
[5] The Peshitta (Syriac translation of the Bible) was the primary one, although there is evidence for his use of a Greek-language and, to a lesser extent, the Syro-Hexapla.
Jacob, however, sought to reconcile this with Aristotle's view of concentric circles, which asserted that the further out one goes, the lighter the elements that they encounter, such that water should not be further out than the air.
For Basil, this was resolved by pointing to the firmament as a solid body that the waters could rest upon, preventing their descent.
In turn, above the upper waters was posited a lighter substance that was composed of a mixture of fire and air.
[9] Jacob's detailed analysis of the nature and hierarchy of the succeeding spheres was greatly influenced by the Carmina Arcana of Gregory of Nazianzus.
[11] An earlier Syriac author, Jacob of Serugh, also took interest in refuting astrology in his own Hexaemeron.
[12] Jacob wrote extensively on the creation and nature of angels, to the degree that it far exceeded the length dedicated to the subject in other Hexameral works.
The sources he engaged with in these conversations in the most detail was the Poemata Arcana by Gregory of Nazianzus, and the Celestial Hierarchy of Pseudo-Dionysius the Areopagite.