Halakhah sa Deuteronomio 16:21: Mishneh Torah, The Chosen Temple, Mishneh Torah, Foreign Worship and Customs, Mishneh Torah, Negative Mitzvot & Sefer HaChinukh

There is to be no visible wood structure in any part of the Temple compound, only stones or bricks and mortar. Even [temporary] wooden walkways in the Court are not allowed.

He who plants a tree near the altar, or anywhere in the entire Court, whether a bare tree or a fruit tree, although he did it to adorn the Temple and beautify it, even such as he shall be striped; for, it is said: "Thou shalt not plant thee an Asherah of any kind of tree beside the altar of the Lord thy God" (Deut. 16.21), because this is the custom of idolaters; they plant trees beside the altar of the idol so as to attract the people to congregate there.¹¹Sifre Deut. 16; Tamid, 28b. C.

It is forbidden to make wooden entrance-passages in the Temple, such as are made in courtyards, the wood being built in and not planted, and the removal from the forbidden appearing to be overmuch, notwithstanding, because it is said: "Any kind of tree"(Ibid.). But all corridors and cornices which were protruding from the walls of the Temple were of stone, not of wood.¹³Sifre, Deut. 16. G.