Baptism

Baptism is a Sacrament which cleanses us from  original sin, makes us Christians, children of God, and heirs of heaven. Christians believe that Baptism is necessary to salvation, because without it we cannot enter into the kingdom of heaven.
 

As such, Baptism is the gateway to life in the Holy Spirit and the door which gives access to the other sacraments.
 

St. Gregory Of Nazianzus said of Baptism:

Baptism is God's most  beautiful and magnificent gift. . . .We call it gift, grace, anointing, enlightenment, garment of immortality, bath of rebirth, seal, and most  precious gift. It is called gift because it is conferred on those who bring nothing of their own; grace since it is given even to the guilty; Baptism because sin is buried in the water; anointing for it is priestly and royal as are those who are anointed; enlightenment because it radiates light; clothing since it veils our shame; bath because it washes; and seal as it is our guard and the sign of God's Lordship.
 

Indeed, this beautiful gift became part of the mandate of Jesus Christ to his Apostles as he sent them out in His name as our first bishops and witnesses to his life, death, and resurrection:

Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, until the end of the age.
Matthew 28:19–20