Covenant of Grace.

Herman Witsius has written:

"The covenant of grace is a compact or agreement between God and the elect sinner; God on his part declaring his free good-will concerning eternal salvation, and every thing relative thereto, freely to be given to those in covenant, by, and for the mediator Christ; and man on his part consenting to that good-will by a sincere faith."

(Witsius, Herman. The Economy of the Covenants Between God and Man, Volume I, Kingsburg, CA: den Dulk Christian Foundation, 1990, pp. 165.)