From Thomas Jefferson Encyclopedia
Pictured to the right is "one of Jefferson's seals," according to his grandson-in-law Nicholas Philip Trist, bearing the motto, "Rebellion to tyrants is obedience to God." Jefferson's Memorandum Books contain the notation, "Pd. Thomson for a seal £3-7" on 26 March 1786; this may refer to the purchase of this seal. The first known intact copy of the seal is on a letter to Richard Gem of 4 April 1790; the seal appears on the frontispiece of Henry Randall's Life of Thomas Jefferson, and can also be seen on one of the gates to the Monticello Graveyard.
"Rebellion to tyrants is obedience to God" was a motto suggested for the Great Seal of the United States, but never used. Jefferson eventually appropriated it for this seal. The ultimate source of the motto is murky, but the best guess of scholars at this point is that Benjamin Franklin probably made it up.
- PTJ 1:677-679, Appendix II: "Bradshaw's Epitaph": The Source of "Rebellion to tyrants is obedience to God."