Grace is freely (gratis) given to the most undeserving and unworthy and is not obtained by any strenuous efforts, endeavors, or works, either samll or great, not even by the efforts of the best and most honorable men who have sougth and followed righteousness with a burning zeal.  (What Luther Says - #1840).

Grace consists in this, that God is merciful to us, shows Himself gracious for the sake of the Lord Christ, forgives all sins, and will not impute them unto us for eternal death.  This is grace: the forgiveness of sins for the sake of the Lord Christ, teh covering up of all sins. 
(What Luther says - #1839).

According to the usage of Scripture, grace signifies that favor of God which wishes us well and justifies us.  That is, it freely grants us the faith which alone justifies us.  Now in the entire Scripture we nowhere read that justification is ascribed to love, since love is rather the fruit of justifying faith (Galatians 5:22): "The fruit of the Spirit is love."  (What Luther says - # 1838).