John Gill Commentary Psalms 148:9

"Mountains and all hills; Fruitful trees and all cedars;" — Psalms 148:9 (ASV)

Mountains, and all hills
Which are originally formed by the Lord, and set fast by his power and strength; these are the highest parts of the earth, and are very ornamental and useful; they include all in them and upon them, the trees and herbage that grow upon them, gold, silver, brass, and iron in them; all very beneficial to mankind, and afford matter of praise to God for them; see (Isaiah 55:12) ;

fruitful trees, and all cedars ;
trees bearing fruit are the fig trees, pomegranates, vines, and olives, with which the land of Canaan abounded; and such as bear lemons, oranges, plums, pears, apples, cherries which produce fruit for the use, pleasure, and delight of man, and so a means of praising God: and "cedars", the trees of the Lord which he has planted; though they bear no fruit, yet very useful in building, and were of great service in the temple at Jerusalem; and which are put for all others of like usefulness, and minister just occasion of praise; see (Psalms 96:12) .