I. Consider what mercy is. (1) Mercy is not to be confounded with mere goodness. Goodness may demand the exercise of justice; mercy asks that justice be set aside. (2) Mercy is a disposition to pardon the guilty. (3) Mercy is exercised only where there is guilt. (4) Mercy can be exercised no further than one deserves punishment.
II. Notice what is implied in trusting in the mercy of the Lord for ever. (1) A conviction of guilt. (2) Trust in mercy implies that we have no hope on the score of justice. (3) Trust in mercy implies a just apprehension of what mercy is. (4) Trust in God's mercy implies a belief that He is merciful. (5) Trusting in the mercy of God "for ever and ever" implies a conviction of deserving endless punishment. (6) Trusting in mercy implies a cessation from all excuses and excuse-making.
III. Consider the conditions upon which we may confidently and securely trust in the mercy of God for ever. (1) Public justice must be appeased. (2) We must repent. (3) We must confess our sins. (4) We must really make restitution as far as lies in our power. (5) We must really reform. (6) We must go the whole length in justifying the Law and its penalty. (7) No sinner can be a proper object of mercy who is not entirely submissive to all those measures of the government that have brought him to conviction.
IV. Notice some mistakes into which sinners fall. (1) Many really trust in justice, and not in mercy. (2) Many trust professedly in the mercy of God without fulfilling the conditions on which only mercy can be shown. (3) Sinners do not consider that God cannot dispense with their fulfilling these conditions. (4) Many are defeating their own salvation by self-justification. (5) Many pretend to trust in mercy who yet profess to be punished for their sins as they go along. (6) Some are covering up their sins, yet dream of going to heaven. (7) We cannot reasonably ask for mercy beyond our acknowledged and felt guilt, and they mistake fatally who suppose that they can.
C. G. Finney, Sermons on Gospel Themes,p. 19.
References: Psalms 52:8. Spurgeon, Morning by Morning,p. 230. Psalms 52 A. Maclaren, Life of David,p. 72.Psalms 53:1. J. Budgen, Parochial Sermons,vol. ii., p. 16.