"I Am the True Vine" comes from the New Testament Gospels, John 15:1, "I am the true vine, and my Father is the vine-dresser":

from http://bible.cc/john/15-1.htm

"I am the true vine and my Father is the farmer.
I am the true vine and my Father is the husbandman.
I am the true vine and my Father is the gardener.
I am the true vine and my Father is the husbandman.
I am the true vine and my Father is the husbandman.
I am the true vine and my Father is the husbandman.
"I am the Vine- the True Vine, and my Father is the vine-dresser.
I am the true vine, and my Father is the husbandman.

With the title "I Am the True Vine," a composition of that name, composed by the Persian Christian composer and poet Bogoroditse Djevo, appears in the Arvo Pärt album (and sheet music), "I Am the True Vine."