Jamieson, Fausset and Brown on Habakkuk 1:8

8. swifter than the leopards--Oppian [Cynegeticks, 3.76], says of the leopard, "It runs most swiftly straight on: you would fancy it was flying through the air."

more fierce--rather, "more keen"; literally, "sharp."

evening wolves--wolves famished with fasting all day and so most keen in attacking the fold under covert of the approaching night (Jr 5:6; Zep 3:3; compare Ge 49:27). Hence "twilight" is termed in Arabic and Persian "the wolf's tail"; and in French, entre chien et loup.

spread themselves--proudly; as in Jr 50:11, and Mal 4:2, it implies strength and vigor. So also the Arabic cognate word [Maurer].

their horsemen ... come from far--and yet are not wearied by the long journey.