Bible (especially the Pauline Epistles/New Testament)
"The Collected Works of St. John of the Cross" translated by Kavanaugh & Rodriguez
"The Cloud Of Unknowing"
"Carthusian Spirituality: The Writings Of Hugh Of Balma And Guigo De Ponte" [The Classics Of Western Spirituality]
"John Ruusbroec: The Spiritual Espousals And Other Works" [The Classics Of Western Spirituality]
"God is faithful, by whom you were called into the fellowship of His Son, Jesus Christ our Lord" 1 Corinthians 1:9
"that which we have seen and heard we declare to you, that you also may have fellowship with us; and truly our fellowship is with the Father and with His Son Jesus Christ. And these things we write to you that your joy may be full" 1 John 1:3,4
"For we do not have a High Priest who cannot sympathize with our weaknesses, but was in all points tempted as we are, yet without sin. Let us therefore come boldly to the throne of grace, that we may obtain mercy and find grace to help in time of need" Hebrews 4:15,16