SB 8.16.31
namo dvi-sirsne tri-pade
catuh-srngaya tantave
sapta-hastaya yajñaya
trayi-vidyatmane namah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
I offer my respectful obeisances unto You, the Supreme Personality of Godhead, who have two heads [prayaniya and udayaniya], three legs [savana-traya], four horns [the four Vedas] and seven hands [the seven chandas, such as Gayatri]. I offer my obeisances unto You, whose heart and soul are the three Vedic rituals [karma-kanda, jñana-kanda and upasana-kanda] and who expand these rituals in the form of sacrifice.