A.T. Robertson Commentary Titus 3:5

"not by works [done] in righteousness, which we did ourselves, but according to his mercy he saved us, through the washing of regeneration and renewing of the Holy Spirit," — Titus 3:5 (ASV)

Done (not in the Greek, only the article των), "not as a result of works those in righteousness which we did." Same idea as in Ro 3:20f.

According to his mercy he saved us (κατα το αυτου ελεος εσωσεν). See Ps 109:26; 1 Peter 1:3; Ephesians 2:4. Effective aorist active indicative of σωζω.

Through the washing of regeneration (δια λουτρου παλινγενεσιας). Late and common word with the Stoics (Dibelius) and in the Mystery-religions (Angus), also in the papyri and Philo. Only twice in the N.T. (Matthew 19:28 with which compare αποκαταστασια in Ac 3:21, and here in personal sense of new birth). For λουτρον, see Eph 5:26, here as there the laver or the bath. Probably in both cases there is a reference to baptism, but, as in Ro 6:3-6, the immersion is the picture or the symbol of the new birth, not the means of securing it.

And renewing of the Holy Spirit (κα ανακαινωσεως πνευματος αγιου). "And renewal by the Holy Spirit" (subjective genitive). For the late word ανακαινωσις, see Ro 12:2. Here, as often, Paul has put the objective symbol before the reality. The Holy Spirit does the renewing, man submits to the baptism after the new birth to picture it forth to men.