Explanatory Notes on the Whole Bible, by John Wesley, [1754-65], at sacred-texts.com
psa 3:2My soul - Of me: the soul being commonly put for the person. In God - God hath utterly forsaken him. Selah - This word is no where used but in this poetical book, and in the song of Habakkuk. Probably it was a musical note, directing the singer either to lift up his voice, to make a pause, or to lengthen the tune. But withal, it is generally placed at some remarkable passage; which gives occasion to think that it served also to quicken the attention of the singer and hearer.
psa 3:3A shield - My defence. My glory - Thou hast formerly given, and wilt farther give occasion of glorying in thy power and favour. Lifter up - Thou wilt restore me to my former power and dignity.
psa 3:4His hill - Out of heaven, so called, Psa 15:1.
psa 3:5Slept - Securely, casting all my cares upon God. Awaked - After a sweet and undisturbed sleep.
psa 3:7Cheek bone - Which implies contempt and reproach. Teeth - Their strength and the instruments of their cruelty. He compares them to wild beasts.