Bhagavad Gita · 10.35

बृहत्साम तथा साम्नां गायत्री छन्दसामहम्।मासानां मार्गशीर्षोऽहमृतूनां कुसुमाकरः॥

bṛihat-sāma tathā sāmnāṁ gāyatrī chhandasām aham māsānāṁ mārgaśhīrṣho 'ham ṛitūnāṁ kusumākaraḥ

Among the Sama Veda hymns, I am the Brihatsama. Among poetic meters, I am Gayatri. Among months, I am Margashirsha (November-December). Among seasons, I am flower-bearing spring.

— Bhagavad Gita 10.35

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)