Early in Mother Teresa's career she was inspired by Jesus' last words on the cross "I thirst" and his discussion with the Samaritan woman at the well, where he asked her for something to drink (John 4:9). The words "I Thirst" became the motto for the Sisters of Charity and would later be found painted or written in every chapel of the society. In Kathryn Spink's biography of Mother Teresa she says this about the motto and its significance:
The Congregation's expressed aim, was to 'quench the infinite thirst of Jesus Christ on the Cross for love of souls'. The importance given to this general aim would be underlined by the fact that in time each one of the Society's chapels throughout the world would be inscribed with the two simple words: 'I thirst'. ... Beyond this lay Mother Teresa's conviction that when Jesus Christ spoke the words 'I thirst' on the cross, he did so as a revelation of God's longing to draw humanity to himself. She saw the cry as an expression of the same thirst revealed to the woman at Jacob's Well, a thirst which could not be quenched by water alone but by love. She also recognized that the requisite love could only come from God.
In a letter written to Sister Jacqueline de Decker, Mother Teresa said:
What a beautiful vocation is yours - A Missionary of Charity - a carrier of God's love - we carry in our body and soul the love of an infinite thirsty God - and we - you and I and all the dear Sisters and the Sick and Suffering will satiate the burning thirst - you with your untold suffering, we with hard labour, but are we not the same one - 'as your Father in me and I in you', said Jesus.
God thirsts. God thirsts for us and humanity thirsts for God. Lord give us that water to drink that will quench our thirst and then yours as well.
. You can also listen to the presentations on Wheaton's website: 
has many beautiful color prints of these amazing works of art.