Mercy and truth preserve the king
Which are two good qualifications in a prince; not ruling his subjects with rigour and cruelty, but with tenderness and clemency; easing them as much as he can of burdens and pressures; showing compassion to the distressed, and pardoning delinquents when the case will admit of it; as also being faithful to his word, promises, and engagements; inviolably adhering to the laws and constitution of the nation, and steady in his administrations of justice; these preserve him in the affections of his people, and make him safe and secure on his throne; and because of these the Lord preserves him from his enemies. It maybe rendered, "grace and truth" F12; and applied to Christ, who is full of both, and which are said to preserve him, ( Psalms 40:11 ) ; and his throne is upholden by mercy;
this explains what is meant by the preservation of him, and what is the security of his throne and kingdom, which is clemency and goodness to his subjects.