A.T. Robertson Commentary Titus 3:6

"which he poured out upon us richly, through Jesus Christ our Saviour;" — Titus 3:6 (ASV)

Which (ου). Genitive case by attraction from ο (grammatical gender) to the case of πνευματος αγιου. We do not have grammatical gender (only natural) in English. Hence here we should say "whom," even if it does not go smoothly with εξεχεεν (he poured out, second aorist active indicative of εκχεω). The reference is to the great Pentecost (Acts 2:33) as foretold by Joel (Joel 2:28).

Richly (πλουσιως). Then and to each one in his own experience. See Ro 10:12; 1 Timothy 6:17.