Which of these religions is the oldest?

Adherents hold that Hinduism—one of the principal faiths in the modern world, with about one billion followers—is the world’s oldest religion, with complete scriptural texts dating back 3,000 years. The oral tradition that gave rise to the Mahabharata, for example, probably dates to about 850 BCE, although its written Sanskrit form is about 400 years younger.

Source: Britannica