Charles Ellicott Commentary 2 Kings 17:9

"And the children of Israel did secretly things that were not right against Jehovah their God: and they built them high places in all their cities, from the tower of the watchmen to the fortified city;" — 2 Kings 17:9 (ASV)

Did secretly. —The literal sense is covered. In this connection it is natural to remember that Heb. verbs of covering and hiding are often used in the sense of dealing perfidiously or deceitfully. (Compare mâ’al, 1 Chronicles 10:13, with me’îl, “mantle; ” and bâgad, “to deal treacherously,”Hosea 5:7, with bèged, “garment.”) The form in the text (the pihel of ‘hâphâ) is only found here.

They built them high places. —First, the institution of unlawful places of worship.

From the tower of the watchmen to the fenced city. —The towers are such as are mentioned in 2 Chronicles 26:10. Here, and in 2 Kings 18:8, these solitary buildings, tenanted by a few herdsmen, are contrasted with the embattled cities which protected multitudes. Wherever men were, whether in small or large numbers, these high places were established.