The sure mercies of David: or, a second part of Heart-treasure : Wherein is contained the supream and substance of gospel-mercies purchased by Christ, and promised in the covenant of grace, together with the several ways how they are made and are to be improved for the saints fort and defence, settlement and incouragement in shaking and back-sliding times. Being the fruit of some meditations upon Isa. 55. 3. By O. Heywood an unprofitable minister of the gospel.