He was speaking about the Spirit, whom those who believed in Him were later to receive. For the Spirit had not yet been given, because Jesus had not yet been glorified.
Textus Receptus (TR) - John 7:39 >Τοῦτο δὲ εἶπε περὶ τοῦ πνεύματος οὗ ἔμελλον λαμβάνειν οἱ πιστεύοντες εἰς αὐτόν· οὔπω γὰρ ἦν πνεῦμα ἅγιον, ὅτι ὁ Ἰησοῦς οὐδέπω ἐδοξάσθη.