27. neighings—(Jer 5:8), image from the lust of horses; the lust after idols degrades to the level of the brute.
hills—where, as being nearer heaven, sacrifices were thought most acceptable to the gods.
wilt thou not … ? when—literally, "thou wilt not be made clean after how long a time yet." (So Jer 13:23). Jeremiah denies the moral possibility of one so long hardened in sin becoming soon cleansed. But see Jer 32:17; Lu 18:27.