In fact, I looked at a large church in our areas website today and it clearly states that "Baptism by immersion in water is what completes the newbirth."  This seems in opposition to Pauls statement in Phil. 3:9 that his righteousness is "through God by faith".  He has no confidence in the flesh.  If his confidence was in the fact that he was baptized I would think that he would have mentioned it somewhere here.   Rather in this passage he is warning us that there will be those who will add to the gospel thereby perverting it.  In fact in the book of Galatians there were those adding to the gospel and causing problems for the church and Paul emphatically stated twice in Gal. 1:8-9  "if anyone preaches any otther gospel to you than what we have preached to you let him be accursed." 

In who or what are you trusting for your salvation???