In Judaism and Christianity, Abraham is considered to be the founding father of the Jewish people. In Islam, Mohammed is his direct descendant.
God told Abraham to leave his home and relatives and go to a new country, Canaan (The Promised Land), that God would give to his descendants. These, despite the barrenness of Abraham's elderly wife, would be as numerous as the stars of heaven, and would bring blessing to all the peoples of the earth.
This story of setting out in faith and hope into the unknown is echoed in the experience of Julia Garnet and of all those displaced from their homeland in one way or another.
Abraham's description of himself as a 'stranger and sojourner' actually comes when he is living in Canaan. His wife Sarah has died in Hebron, and he asks the local people for a sepulchre in which to bury her:
And Abraham stood up from before his dead, and spake unto the sons of Heth, saying, I am a stranger and sojourner with you; give me a possession of a burying place with you, that I may bury my dead out of my sight.
The sons of Heth have a lot of respect for Abraham, and readily agree. It is an act of kindness shown to a stranger, similar to the hospitality shown to Miss Garnet in Venice.
The painting is by Jozsef Molnar.