एषां भूतानां पृथिवी रसः पृथिव्या अपो रसः ।अपामोषधयो रस ओषधीनां पुरुषो रसः पुरुषस्य वाग्रसो वाच ऋग्रस ऋचः साम रसः साम्न उद्गीथो रसः ॥ १.१.२ ॥
In plain words
The essence of these beings is the earth; the essence of the earth is the waters; the essence of the waters is the plants; the essence of the plants is man; the essence of man is speech; the essence of speech is the Ṛc; the essence of the Ṛc is the Sāman; the essence of the Sāman is the Udgītha.