The expression is found in the Testament of Levi.
Test. Levi 18.11 wrote:καὶ δώσει τοῖς ἁγίοις φαγεῖν ἐκ τοῦ ξύλου τῆς ζωῆς, καὶ πνεῦμα ἁγιωσύνης ἔσται ἐπ’ αὐτοῖς.
It is also found among 3rd century and later Patristic authors, usually quoting Rom 1:4.
Stephen C. Carlson, Ph.D. (Duke)
Post-Doctoral Fellow, Faculty of Theology, Uppsala