A.T. Robertson Commentary John 14:12

"Verily, verily, I say unto you, he that believeth on me, the works that I do shall he do also; and greater [works] than these shall he do; because I go unto the Father." — John 14:12 (ASV)

Shall he do also (κακεινος ποιησε). Emphatic pronoun εκεινος, "that one also."

Greater works than these (μειζονα τουτων). Comparative adjective neuter plural from μεγας with ablative case τουτων. Not necessarily greater miracles and not greater spiritual works in quality, but greater in quantity. Cf. Peter at Pentecost and Paul's mission tours. "Because I go" (οτ εγω πορευορνα). Reason for this expansion made possible by the Holy Spirit as Paraclete (16:7).