Midrash su I Re 10:17

R. Isaac b. Tubia said in the name of Rab: "Why is the Temple called Lebanon? Because it cleanses the sin of Israel." R. Zutra said: "Why is the Temple called Ya'ar (forest), as it is written (I Kings 10, 17) … and the King put the in the house of the forest of Lebanon? Just as the forest produces sprouts, so does the Temple produce sprouts; for R. Oshiya said (Ib. b.): 'At the time when Solomon built the Temple, he planted there all kinds of golden fruit-trees, and they bore fruit at proper times; and whenever the wind blew on them, they fell down ripe, as it is said (Ps. 72, 16) Its fruits shall shake like the trees of Lebanon. And this served as a support for the priests, but when the heathens had entered the Temple, the fruit-trees became withered, as it is said (Nahum 1, 4) The flowers of Lebanon wither. In the future the Holy One, praised be He! will restore them, as it is said (Is. 35, 2) It shall blossom abundantly and rejoice; yea, with joy and singing, the glory of Lebanon shall be given unto it.' "

“I made myself pools of water to irrigate from them a forest which grows trees” (Ecclesiastes 2:6).
“I made myself pools of water” – an irrigation system; “to irrigate from them a forest which grows trees” – this is the Land of Israel, as it is stated: “[Three hundred shields of gold…] The king placed them in the house of the forest of Lebanon” (II Chronicles 9:16).¹⁶The shields were kept in the Land of Israel; hence, the Land of Israel is referred to as a forest.