Bhagavad Gita 10.35
बृहत्साम तथा साम्नां गायत्री छन्दसामहम्। मासानां मार्गशीर्षोऽहमृतूनां कुसुमाकरः।।10.35।।
bṛhatsāma tathā sāmnāṃ gāyatrī chandasāmaham| māsānāṃ mārgaśīrṣo'hamṛtūnāṃ kusumākaraḥ||10.35||
brihatsama tatha samnam gayatri chandasamaham masanam margashirsho'hamritunam kusumakarah10.35
Meaning
Among hymns, He is the Brihat-sama; among Vedic meters, He is Gayatri; among months, He is Margashirsha; and among seasons, He is spring.
सामों में मैं बृहत्साम और छन्दों में गायत्री छन्द हूँ; मैं मासों में मार्गशीर्ष और ऋतुओं में वसन्त हूँ।
This is verse 35 of 42 in Chapter 10 (Vibhooti Yoga) of the Bhagavad Gita.