The concept of two spiritual powers is far older than Second Temple Judaism and its Christian offshoot.
The concept's roots are believed to have derived from Zoroastrianism ...
Zoroastrianism,[n 1] or more natively Mazdayasna,[1] is one of the world's oldest religions, "combining a cosmogonicdualism and eschatological monotheism in a manner unique […] among the major religions of the world."[2] Ascribed to the teachings of the Iranian prophet Zoroaster (or Zarathustra),[3] he exalted their deity of wisdom, Ahura Mazda (Wise Lord), as its Supreme Being.[4] Leading characteristics, such as messianism, heaven and hell, and free will are said to have influenced other religious systems, including Second Temple Judaism, Gnosticism, Christianity, and Islam.[5] With possible roots dating back to the second millennium BCE, Zoroastrianism enters recorded history in the 5th-century BCE,[4] and including a Mithraic Median prototype and Zurvanist Sassanid successor it served as the state religion of the pre-Islamic Iranian empires from around 600 BCE to 650 CE. Zoroastrianism was suppressed from the 7th century onwards following the Muslim conquest of Persia.[6] ... In Zoroastrianism, the creator Ahura Mazda, through the Spenta Mainyu (Good Spirit, "Bounteous Immortals")[11] is an all-good "father" of Asha (Truth, “order, justice,")[12][13] in opposition to Druj(“falsehood, deceit”)[14][15] and no evil originates from "him".[16] "He" and his works are evident to humanity through the six primary Amesha Spentas[17] and the host of other Yazatas, through whom worship of Mazda is ultimately directed.
Reference: https://en.wikipedia.org/wiki/Zoroastrianism
Sometimes this concept is referred to as 'dualism,' and is noticeable in the Dead Sea Scrolls.
It is believed that the Jewish elite came into contact with Zoroastrian concepts while in exile in Babylon (lots of time on their hands to speculate) especially after Cyrus the Iranian conquered Babylon.
The spiritual idea of light and darkness is another Zoroastrian belief that was effectively copied by the Christian offshoot we know as Manicheanism