The hills were covered with the shadow of it - That is, It made a shade, by its luxuriant foliage, on the hills in every part of the land; it seemed to cover all the hills.
And the boughs thereof were like the goodly cedars - Margin, as in Hebrew, cedars of God; that is, lofty, majestic cedars. See the notes at Psalm 65:9. The reference here is to the cedars of Lebanon, among the most majestic objects known to the Hebrews.

The hills were covered -
6. The vine, carefully cultivated in a suitable soil, may be spread to any extent. In the land of Judea it formed shades under which the people not only sheltered and refreshed themselves in times of sultry heats; but it is said they even ate, drank, and dwelt under the shelter of their vines. See 1-Kings 4:25; Micah 4:4; 1 Maccabees 14:12. God so blessed the Jews, particularly in the days of David and Solomon, that all the neighboring nations were subdued - the Syrians, Idumeans, Philistines, Moabites, and Ammonites.

The hills were covered with the shadow of it,.... Alluding to the land of Canaan, which was a mountainous and hilly country, at least some part of it; hence we read of the hill country of Judea, Luke 1:39 and to the nature of vines, which delight to grow on hills and mountains (p): in a figurative sense this may denote the subjection of kings and kingdoms, comparable to hills, to the Israelites in the times of David and Solomon, 2-Samuel 8:1 and the exaltation of the church of Christ, in the latter day, over the hills and mountains, Isaiah 2:2. The Targum is,
"the mountains of Jerusalem were covered with the shadow of the house of the sanctuary, and of the houses of the schools:''
and the boughs thereof were like the goodly cedars; to these the righteous are compared, Psalm 92:13, the Targum is,
"the doctors, the mighty preachers, who are like to the strong cedars:''
the words may be rendered, "the boughs thereof cover the goodly cedars", or "cedars of God" (q); that is, overrun and overtop the goodly cedars; alluding to vines running and growing upon high and goodly trees; and so may denote, as before, the power of Israel over the princes and potentates of the earth, comparable to cedars, the most excellent; as things most excellent have often the name of God added to them; see Psalm 104:16.
(p) "Bacchus amat colles----" Virgil Georgic. l. 2. v. 113. (q) "rami ejus cedros Dei", Tigurine version; so Sept. "et ramia ejus cedri Dei", Musculus, Cocceius; "palmitibus ejus cedri altissimae operiebantur", Piscator, De Dieu; "ramis ejus opertae sunt cedri Dei", Michaelis.

The hills - They filled not only the fruitful valleys, but even the barren mountains.