Adam Clarke on Titus 3:6

Which he shed on us abundantly - Οὑ εξεχεεν· Which he poured out on us, as the water was poured out on them in baptism, to which there is here a manifest allusion; but as this was sometimes only sprinkled on the person, the heavenly gift was poured out, not in drops, but πλουσιως, richly, in great abundance.

Through Jesus Christ - Baptism is nothing in itself; and there had been no outpouring of the Holy Spirit, had there been no saving and atoning Christ. Through him alone all good comes to the souls of men.