The Sacrament of Baptism is one instituted by Christ in the Gospels when He makes of Himself an example being cleansed with water at the hands of John the Forerunner (or known as John the Baptizer). The command was given then that Baptism should be administered in the name of The Father, and The Son, and The Holy Ghost, thus instituting the modern Trinitarian formula for the sacrament. The historical theology of Baptism is that Original Sin is passed to a child by his parents, just as any other trait would be. Because of this understanding it is understood to be the responsibility of a parent to have it washed away. Not dissimilar to feeding, bathing, and dressing, Baptism is a choice made by the parents of a child for his or her benefit. At Baptism a child's parents (and often godparents) make solemn vows to raise the child, teaching them the doctrines and traditions of the faith, so that in due time the child may confirm before a bishop that he or she has accepted and believes that which they have been taught. 

The Gospel according to St. Matthew, Chapter 28, Verses 18-20

The Authorized Version (KJV):

18 And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth. 

19 Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: 

20 teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you always, even unto the end of the world. Amen.