John Trapp on Job 39:18

Verſe 18. What time ſhe lifteth up her ſelf on high, &c.] That is, when ſhe runneth away from the hunter (which ſhe doth with ſingular ſwiftneſs) ſhe lifteth up her ſelf on high, not from the earth, as other birds (for that ſhe cannot do) but on the earth, with wings ſtretcht out like ſailes, and her whole body bolt upright, ſcarce touching the earth at all with her feet, but quickning her own pace with ſharp ſpurs, which they ſay ſhe hath in the pinnion of each wing, ſo pricking her ſelf on, that ſhe may run the faſter; to teach us what we ſhould do in the race of Religion, and when purſued by Satan, how to haſten to Chriſt.

She ſcorneth the horſe and his rider] That is, ſhe eaſily out-runs them, being as ſwift as a bird that flyeth. They ſay, the Arabians are wont to try their horſes ſwiftneſs by trying to overtake them.