पुरुषो वा अग्निर्गौतम तस्य व्यात्तमे-व समित्प्राणो धूमो वागर्चिश्चक्षुरङ्गाराःश्रोत्रं विस्फुलिङ्गास्तस्मिन्नेतस्मिन्नग्नौ दे-वा अन्नं जुह्वति तस्या आहुत्यै रेतः सं-भवति ॥ १२ ॥
In plain words
Man himself is a fire, Gautama. His open mouth is its fuel, the breath moving through him its smoke, his speech its flame, his eye its coals, his ear its scattering sparks. Into this fire the gods pour food as their offering -- and from that offering, seed is born.
Close to the Sanskrit
Man, indeed, is a fire, O Gautama; his open mouth alone is the fuel; the vital breath is the smoke; speech is the flame; the eye is the coals; the ear is the sparks. In this, in this very fire, the gods offer food. From that oblation, semen arises.