Baptism is the sign and seal of the Lord Jesus Christ.  Jesus through his own baptism identified himself with sinners in order to fulfill all righteousness.  In His baptism Jesus was attested son by the Father and was anointed with the Holy Spirit to undertake the way of the servant. 
Jesus the risen Lord assured his followers of his continuing presence and power and commissioned them "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, and teaching them to obey everything that I have commanded you.  And remember, I am with you always to the end of the age."  Matthew 28:19, NRSV. 
In baptism we participate in Jesus Christ's death and resurrection.  We die to what separates us from God and are raised to newness of life in Christ.  Baptism points us back to the grace of God expressed in Jesus Christ who died and was raised for us.  Baptism points us forward to that same Christ who will fulfill God's purpose in God's promised future. 
Both believers and their children are included in God's covenant of love.  Infant children are thus baptized without undue delay but also without undue haste since parents should be committed to living a Christian lifestyle.  For older children and adults baptism is admitted to those who profess their faith.