“A principle of works — do this and live — governed the attainment of the consummation-kingdom proferred in the blessing sanction of the creational covenant. Heaven must be earned. According to the terms stipulated by the Creator it would be on the ground of man’s faithful completion of the work of probation that he would be entitled to enter the Sabbath rest. If Adam obediently performed the assignment signified by the probation tree, he would receive, as a matter of pure and simple justice, the reward symbolized by the tree of life. That is, successful probation would be meritorious. With good reason then covenant theology has identified this probation arrangement as a covenant of works, thereby setting it in sharp contrast to the Covenant of Grace.”
Kingdom Prologue: Genesis Foundations for a Covenantal Worldview, [Eugene, OR]: M.G. Kline, 2006.