Covenant of Nature
The covenant of nature is that which God the Creator made with innocent man as his creature, concerning the giving of eternal happiness and life under the condition of perfect and personal obedience. It is called “natural,” not from natural obligation (which God does not have towards man), but because it is founded on the nature of man (as it was at first created by God) and on his integrity or powers.
Francis Turretin, Institutes of Elenctic Theology, ed. James T. Dennison Jr., trans. George Musgrave Giger, vol. 1 (Phillipsburg, NJ: P&R Publishing, 1992–1997), 575.