According to Titus 3:5, God saved us not by righteous deeds we had done but according to what?

Answer: His mercy

He saved us, not by the righteous deeds we had done, but according to His mercy, through the washing of new birth and renewal by the Holy Spirit.

“But when the kindness of God our Savior and His love for mankind appeared, He saved us, not by the righteous deeds we had done, but according to His mercy, through the washing of new birth and renewal by the Holy Spirit.”— Titus 3:4-5 (BSB)