Valmiki Ramayana Yuddha Kanda Sarga 86 Shloka 18

तस्मिन् काले in the meantime, धरणीधरसङ्काशः who resembled mountain, अरिन्दमः tamer of enemies, हनुमान् Hanuman, सुदुरासदम् difficult to overpower, महावृक्षम् huge tree, उद्यम्य taking up, राक्षसानाम् at Rakshasas, तत् those, सैन्यम् army, कालाग्निरिव like fire at dissolution, निर्दहन् created havoc, सःhe, वानरःVanara, युधि in combat, बहुभिः many, वृक्षैः trees, निःसज्ञम् fighting, चकार went about

In the meantime, Hanuman, who resembled a mountain, a tamer of enemies, who is difficult to overpower, taking up huge trees fighting with Rakshasas created havoc like fire at the time of dissolution and went about.