The first command is to PREACH ...the 2nd command is that the men MUST BELIEVE only then are they baptized..
The saving act is the believing
Jhn 3:36 He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
Jhn 6:29 Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent.
Jhn 11:26 And whosoever liveth and believeth in me shall never die. Believest thou this?
Baptism was a symbolic Jewish rite of conversion ..it symbolized repentance and cleaning