Abraham called himself a stranger. (Genesis 23:4): "A stranger and a sojourner am I with you." David called himself a stranger. (Psalms 119:19): "I am a stranger in the land." And again (1 Chronicles 29:15): "For we are strangers before You and sojourners as all of our ancestors. As a shadow are our days upon the earth, without a prospect." And (Psalms 39:13): "For a stranger am I with You, a sojourner as all of my ancestors."
The Mekhilta assembles these verses to establish a remarkable pattern. The greatest figures in Jewish history — the founding patriarch and the greatest king — both identified themselves as strangers. Abraham used the term when negotiating to buy a burial plot in Hebron. David used it when reflecting on the transience of human life before God.
If Abraham and David were strangers, then everyone is a stranger. No one can claim permanent, rooted ownership of their place in the world. Every person is passing through. Every generation is temporary. The land itself belongs to God, and its human inhabitants are guests.
This teaching connects the legal protection of converts to a universal theological insight. The Torah commands Israel to love the stranger because Israel's own heroes understood themselves as strangers. The convert who arrives in the community without roots is not an anomaly. He is the most honest expression of what every human being actually is — a temporary resident in a world that belongs to God.