John Gill Commentary Titus 3:6

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

Which he shed on us abundantly
"Or richly"; either which love he shed abroad in the hearts of those whom he regenerated and renewed by his Spirit; or which water of regeneration, that is, grace, comparable to water, he plentifully shed, and caused to abound where sin had done; or rather whom, or which Holy Spirit, with his gifts and graces, such as faith, hope, and love, and every other, he poured forth in great abundance on them; see (Isaiah 44:3) (1 Timothy 1:14)

through Jesus Christ our Saviour ;
the love and kindness of God the Father our Saviour, comes through him; the mercy of God streams through him; the salvation itself is by, and through him; the grace communicated in regeneration and renovation is out of his fulness; the Spirit himself is given forth from him; and every supply of grace, by which the work is carried on, comes out of his hands; and everything wrought in us, that is well pleasing in the sight of God, is through him; and even the gift of God, eternal life itself.