As I have given you the passage from Philippians that shows being "in Him" is by faith alone. And since it is impossible for an infant to excercise faith ... being "in Him" cannot be as a result of water baptism, ... which imples that the baptism mentioned in your passages CANNOT refer to water baptism.
the verses from Phillipians say righteousness is by faith, not being placed “in Christ” the Bible is very clear this only happens by baptism.
besides, faith is a work and we know we are not saved by works. faith is something we do, therefore a work.
baptism is by the Holy Spirit, thru the Church and it is done to us, not by us.