Rigveda 1.164.45

४च॒त्वारि॒ वाक् परि॑मिता प॒दानि॒ तानि॑ विदुर्ब्राह्म॒णा ये म॑नी॒षिण॑: ।गुहा॒ त्रीणि॒ निहि॑ता॒ नेङ्ग॑यन्ति तु॒रीयं॑ वा॒चो म॑नु॒ष्या॑ वदन्ति॥

4catvāri vāk parimitā padāni tāni vidurbrāhmaṇā ye manīṣiṇa: |guhā trīṇi nihitā neṅgayanti turīyaṃ vāco manuṣyā vadanti ||

Our plain-language meaning of this verse is waiting for scholar review.