श्रोत्रमेवर्ङ्मनः साम तदेतदेतस्यामृच्यध्यूढंसाम तस्मादृच्यध्यूढंसाम गीयते । श्रोत्रमेव सा मनोऽमस्तत्साम ॥ १.७.३ ॥
śrotramevarṅmanaḥ sāma tadetadetasyāmṛcyadhyūḍhaṃsāma tasmādṛcyadhyūḍhaṃsāma gīyate | śrotrameva sā mano’mastatsāma || 1.7.3 ||
3. The organ of hearing is the Ṛk, and the mind is Sāma. This Sāma [called the mind] is based on the Ṛk [called the organ of hearing]. This is why Sāma scholars sing songs based on the Ṛk. The organ of hearing is sā, and the mind is ama. Together they are Sāma.
Word-for-word explanation:
Śrotram eva ṛk, the organ of hearing is the Ṛg Veda; manaḥ sāma, the mind is the Sāma; tat etat sāma, this Sāma [called the mind]; etasyām ṛci adhyūḍham, is based on the Ṛk [the organ of hearing]; tasmāt, this is why; ṛci adhyūḍham sāma gīyate, the Sāma is sung as based on the Ṛk; śrotram eva sā, the organ of hearing is sā; manaḥ amaḥ, the mind is ama; tat sāma, that [if joined together] is Sāma.
Commentary:
The mind is said to be the Sāma because it controls the organ of hearing.