Charles H. Spurgeon on Psalms 101:1

Mercy and judgment. As the pedge of the ship S.Paul sailed in was Castor and Pollux, twin brothers, so the badge of this Psalm is Mercy and Judgment, inseparable companions; of whom it may be said, as our prophet sometimes spake of Saul and Jonathan, "They were lovely and pleasant in their lives, and in their deaths they were not divided." These are the two brightest stars in the firmament of majesty; the two fairest flowers, and choicest jewels in the imperial crown; like the carnation and the lily, the ruby and the sapphire, or the carbuncle and the diamond, yielding a mutual and interchangeable lustre each to other. They resemble not unfitly the two supporters of the king's arms, or the two seraphim stretching out their golden wings over the propitiatory, or the white and red rose in the same escutcheon.

We read that Solomon set up two goodly pillars in the porch of the temple, the one called Jachin, the other Boaz, which signify stability and strength; such pillars of the state are mercy and judgment. The throne of the King is borne up by them, as Solomen's was with lions of ivory on each side. Therefore I as in one place it is said that "the throne is established by justice" (Pr 16:12); so in another that it is "upheld by mercy" (Pr 20:28); justice being as the bones and sinews in the body politic, and mercy as the veins and arteries. They are the two hands of action, the two eyes of virtue, and the two wings of honour. And as the eyes, if they be rightly set, do both look one way; so do mercy and judgment, however in the apprehension of the vulgar they seem to look contrary ways. And as the treble and the bass accord best music; so do they in managing the commonwealth. Wherefore David promiseth to make them both sound tunable in his song without jar or discord: "I will sing of mercy and judgment." ...

As mercy is here set in the first place; so shall the sentence of mercy and absolution be first pronounced at the last day. And it is a laudable custom of princes, at their first entrance to their kingdoms, to shew mercy, by hearing the mourning of the prisoner, and delivering the children of death, by loosing the bands of wickedness, by taking off the heavy burdens, by letting the oppressed go free, and by breaking every yoke of former extortions. Thus, our prophet himself, as soon as the crown was settled on his head, made inquiry if there remained yet alive any of the house of Saul, on whom he might shew mercy (2Sa 9:1). O how fair a thing is this mercy in the time of anguish and trouble! It is like a cloud of rain that cometh in the time of drought. But this mercy, here spoken of in the first part of our prophet's song, stretcheth further; unfolding itself in clemency, in courtesy, and in compassion. In clemency, by pardoning malefactors; in compassion, by relieving the afflicted; in courtesy, towards all. —George Hakewill, or Hakewell, 1579-1649.