His mission was to seek and to save that which was lost. Also, baptism doesn't save ( depending on who you talk to of course ). It's an act of obedience. Concerning the Old Testament saints, they were cleansed through faith, just as the New Testament saints were. The Old Testament saints had faith in what was to come ( Christ ) even though the crucifixion and resurrection hadn't happened yet it's coming was evident in the O.T. scriptures... The New Testament saints have faith in what has already happened. The book of Hebrews helps understand this.