James Ussher on the Difference between the Covenants of Works and Grace
Q. What is the first of these Covenants?
A. The Law, or the covenant of works: whereby God promiseth everlasting life unto man, upon condition that he perform intire and perfect obedience unto his Law, according to that strength wherewith he was indued by vertue of his creation; and in like sort threatneth death unto him, if he do not perform the same. . .
Q. What is the second Covenant?
A. The Gospel, or the Covenant of grace; whereby God promiseth everlasting life unto man, upon condition that he be reconciled unto him in Christ: for as the condition of the first, was the continuance of that righteousness which was to be found in mans own person: so the condition of the second is the obtaining of that righteousness which is without himself; even the righteousness of God which is by faith in the Mediator Jesus Christ.
James Usher, A Body of Divinity: Or, the Sum and Substance of Christian Religion, 488, 489-490.