John Calvin Commentary Titus 3:6

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

Which he shed, (or, whom he shed.) In the Greek, the relative pronoun may apply either to the “washing” or to the “Spirit,” for both nouns—λουτρόν and Πνεῦμα—are neuter. It makes little difference to the meaning, but the metaphor will be more elegant if the relative is applied to λουτρόν, the “washing.” Nor is it inconsistent with this opinion that all are baptized without any distinction; for, while he shows that the “washing” is “shed,” he speaks not of the sign, but rather of the thing signified, in which the truth of the sign exists.

When he says, abundantly, he means that the more any of us excels in the abundance of the gifts he has received, so much the more is he under obligation to the mercy of God, which alone enriches us; for in ourselves we are altogether poor and destitute of everything good. If it is objected that not all the children of God enjoy such great abundance, but, on the contrary, the grace of God drops sparingly on many, the answer is that no one has received so small a measure that he may not justly be accounted rich. For the smallest drop of the Spirit (so to speak) resembles an ever-flowing fountain that never dries up. It is therefore a sufficient reason for calling it “abundance” that, however small the portion that has been given to us, it is never exhausted.

Through Jesus Christ. It is he alone in whom we are adopted; and therefore, it is he alone through whom we are made partakers of the Spirit, who is the earnest and witness of our adoption. Paul therefore teaches us by this phrase that the Spirit of regeneration is bestowed on none but those who are members of Christ.