Christian mysticism refers to the development of mystical practices and theory within Christianity. It has often been connected to mystical theology, especially in the Catholic and Eastern Orthodox traditions. The attributes and means by which Christian mysticism is studied and practiced are varied and range from ecstatic visions of the soul's mystical union with God to simple prayerful contemplation of Holy Scripture (i.e., Lectio Divina). This article addresses the practice of the inner, spiritual life within the Christian tradition.
Peter 1:4 says that God enables Christians to be "partakers of the divine nature."
John 17:21 records Jesus' prayer for his followers during the last supper: "You, Father, are in Me, and I in You; [I pray] that they also may be one in Us."
The mystical experience of the apostles, Peter, John, and James, at the Transfiguration of Jesus, is confirmed in each of the Synoptic Gospels.
See, e.g., Mark 9:2-8. Jesus led the three to the top of Mount Tabor. Before the eye of the disciples, he was transformed. His face shone like the sun, and his cloths became brilliant white. Elijah and Moses appeared to them. Then “A cloud came, overshadowing them and a voice came out of the cloud, and said “This is my beloved Son. Listen to him.""
In II Corinthians 12:2-6, St. Paul refers to what tradition says was his own mystical experience, when he speaks of a man who was "caught up to the third heaven." 
In Galatians 2:20, Paul says "It is no longer I who live, but Christ lives in me."
In Ephesians 4:6, Paul writes "[There is] one God and Father of all who is above all and through all and in all.
1 John 4:16: "He who abides in love abides in God, and God in him.
1 Corinthians 6:19: "Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God?"
2 Timothy 1:14: "Guard the good deposit that was entrusted to you—guard it with the help of the Holy Spirit who lives in us."