John Trapp on Psalms 109:6

Verſ. 6. Set thou a wicked man ever him] Whoſe tender mercies may be cruelties: let the Devil be his Task-maſter. Thus he prayeth againſt Doeg, or Ahitophel, but certainly Judas, Act. 1.20. And ſo the primitive Chriſtians prayed againſt Julian the Apoſtate, and afterward againſt Arius the heretick, whoſe death was precationis opus non morbi, Lib. 1. cap. 15. the effect of prayer, rather than of his diſeaſe, ſaith Socrates. We are bound to pray daily, Thy Kingdome come, but muſt be adviſed how we pray, as David here doth, againſt particular perſons: His curſes here and elſewhere are indefinite, or conditional; either he nameth not the man, or intendeth it, if God intend it ſo, or they are non tam vota quam vaticinia, not ſo much prayers as prophecies.

And let Satan (or an Adverſary) ſtand at his right hand] To withſtand him, and get the better of him, as Zach. 3.1. Or, to aggravate his fault before an unjuſt Judge.