כי - טעם ה' שיש לך להטיב הרשע לא תחפוץ, בעבור שהזכיר מלכי. For (כִּי - Ki): The reason (ta'am) [for expecting Ad-nai's help] is that it is Your nature (lecha) to do good; You do not desire wickedness (ha-resha lo tachpotz). [This follows logically] because he mentioned "My King" [in verse 3 - a just king does not tolerate wickedness].
לא יגורך רע - יגור עמך כמו ישכבנה, וככה גדלני כאב גדל עמי ורע הוא אדם לא שם דבר, והעד לא יתיצבו הוללים מלעיגים לנגד עיניך, כמשפט אנשי ארץ. Evil cannot abide with You (לֹא יְגֻרְךָ רָע - lo yegurkha ra): [The verb yegur means] "dwell with You" (yagur imakh). Similar [usage implying close association/dwelling is found in (Job 31:18)]: "[For from my youth] he grew up with me (gedelani) like a father, ... [I] guided her [the widow] (gedel immi)." And ra (רָע - evil) refers to an evil person (adam), not an abstract noun (shem davar - 'a word for a thing' [i.e., evilness]). The proof (ve-ha-ed) is [from the next verse, v. 6]: "The boastful (holelim)/scoffers (mal'igim) shall not stand before Your eyes." [These terms clearly refer to people]. [The phrase "shall not stand before Your eyes"] is according to the manner/custom of the people of the land (ke-mishpat anshei aretz).