Exploring the personal views of key American founders, this chapter reveals their nuanced and often contradictory engagement with Mosaic and Islamic legal traditions on the issue of slavery. John Witherspoon, a signer of the Declaration, explicitly defended “lawful (Mosaic) ways of making slaves” in his Princeton lectures, thereby contributing to the theological rationales that helped entrench slavery in the fledgling nation. Thomas Jefferson, a slaveholder who eloquently professed opposition to slavery while himself continuing and helping perpetuate the inhumane practice, seemingly employed Mosaic legal principles to sanction slave uprisings as a justifiable response to the master’s tyranny, turning the religious precepts of pro-slavery advocates against them. Benjamin Franklin, in his later abolitionist phase, strategically mocked the defenses of American slavery by citing Qur’anic justifications used by North African Muslim rulers turning Islamic law into a satirical mirror of Christian hypocrisy. In contrast, John Adams and John Jay both balanced their private antislavery sentiments with politically expedient actions: Adams, who once helped defend at least two slave owners by appealing to Mosaic and racial arguments, later invoked Mosaic prohibitions against man-stealing to condemn British impressment of white seamen but remained silent on Black slavery. Jay, a lifelong gradualist and founder of the New York Manumission Society employed the Exodus narrative symbolically to endorse his moderate approach, demonstrating how the sacred traditions of Moses and Muhammad were wielded selectively by the founding generation to navigate the profound moral and political contradictions of the early republic. In all of this, these (and other) American founders were profoundly shaped by the debates over both sacred and secular slave law and practice which were significantly intensified amid the rise and fall of “the Spirit of ’76.”