Sāriputta, this is said: ‘A Stream-Enterer, a Stream-Enterer.’

‘What now, Sāriputta, is a Stream-Enterer?’

One who possesses this Noble Eight Fold Path, Venerable Sir, is called a Stream-Enterer: this Venerable One of such a name and clan.

Good, good, Sāriputta! One who possesses this Noble Eight Fold Path is a Stream-Enterer: this Venerable One of such a name and clan.

(Reference: SN 55.5)

In this Teaching from Gotama Buddha, he asks one of his closest Students “Sāriputta”, “What now, Sāriputta, is a Stream-Enterer?”.

Sāriputta replies that one who is a Stream-Enterer is one who is practicing The Eight Fold Path.

The Buddha confirms this is true that for a Practitioner to be a Stream-Enterer, the first Stage of Enlightenment, a Practitioner would need to be practicing or “possesses” The Eight Fold Path.

A Stream-Enterer would have eliminated the first three fetters/taints/pollution of mind which includes “wrong behavior and observances”. This includes a well developed practice of The Eight Fold Path.