Acts 2: 1-11
The coming of the Spirit leads to such a transformation in the disciples that they become enthusiastic and passionate apostles of the Good news, keen and able to communicate with everyone, regardless of barriers posed by different races, nationalities and languages. 

Romans 8: 8-17
Paul stresses the spiritual life as being of paramount importance for those who are Christians. 

John 14: 15-16.23-26
Jesus promises the disciples that they will never be alone, for he will send them an Advocate who will remain with them.  It is the Holy Spirit, who will guide them and teach them how to live as Jesus has taught them.