Final answer:
The oldest source referring to God as Yahweh is the Yahwist text, marking the early monotheistic worship within the Hebrew culture that eventually developed into Judaism.
Step-by-step explanation:
The oldest source in which God is referred to as Yahweh is A. J (Yahwist). The Yahwist religion, a precursor to Judaism, was an evolving monotheistic faith that held a special emphasis on the worship of Yahweh as the patron deity of the Hebrew people. Over time, the belief in Yahweh transformed from henotheism, where multiple gods are acknowledged but only one is worshipped, to monotheism, the belief in the existence of only one god.
In this process, the other gods of surrounding cultures and those within the earlier Canaanite polytheistic traditions were set aside in favor of exclusive worship of Yahweh. The historical development of this worship and its centrality to Hebrew culture, especially post the destruction of the northern kingdom of Israel, reflect the significant role that Yahweh played. This transition is captured within the texts of the Hebrew Bible, which offer insights into the religious history of the period.