16 And in the sixth week, in the fifth year thereof, [1951 A.M.] Abram sat up throughout the night on the new moon of the seventh month to observe the stars from the evening to the morning, in order to see what would be the character of the year with regard to the rains, and he was alone as he sat and observed. 17 And a word came into his heart and he said: 'All the signs of the stars, and the signs of the moon and of the sun are all in the hand of the Lord. Why do I search (them) out? 18 If He desires, He causes it to rain, morning and evening; And if He desires, He withholds it, And all things are in his hand.'
Philo On Abraham 70
70 The man who had been bred up in this doctrine, and who for a long time had studied the philosophy of the Chaldaeans, as if suddenly awakening from a deep slumber and opening the eye of the soul, and beginning to perceive a pure ray of light instead of profound darkness, followed the light, and saw what he had never see before, a certain governor and director of the world standing above it, and guiding his own work in a salutary manner, and exerting his care and power in behalf of all those parts of it which are worthy of divine superintendence.
Notes and References
"... interpreters found an alternate explanation for how Abraham came to know that there is only one God: they connected his refusal to worship "other gods" (implied by Joshua 24:2-3) with his knowledge of the stars. Somehow, Abraham came to understand that it is not the stars but God who controls human destiny ... And so, the motif 'Abraham the Astronomer'—based on the simple fact that the Bible names Chaldea as Abraham's birthplace—led to a new motif, one that explained how Abraham came to be a monotheist: it was Abraham's knowledge of astronomy and observations of the heavens that led him to discover that there is only one God ..."
Kugel, James L. The Bible as it Was (pp. 140-141) Harvard University Press, 1998