We know that the Vedas are considered most basic and important scripture of Hinduism. Vedas are believed to be words from Ishvara (अपौरुषेय). And the Upanishads are the part of Vedas which are full of spiritual knowledge and are known as Vedanta.
So, I am looking for praises (स्तुति) to Vedas & Upanishads which may have been composed by sages.
I am here with providing partial answer of your question with " Praising of Upanishads" (upanishad Stuti , उपनिषद् स्तृती).
There is a chapter in Shreemad Bhagvad purana called "Veda Stuti" or Praising of Vedas. See chapter 87 ,Verse 3 , (Gita press Gorakgpur version) in which shree shuka deva is Praising Upanishadas. As -
सैषा हयुपनिषद ब्राह्मी पूर्वेषा पूर्वजै धृर्ता । श्रद्धया धारयेद यस्तां क्षेमं गच्छेद किंश्चनः
Sesha Hyupanishad Brahmi Purvesham PurvajaiDhruta l Shradhyaha Dharayed Shkemam GacheeddaKincshanaha ll
Meaning - Sanakadi Rishi ,who are ancestors of ancestors , accepted this hign knowladge of Upanishadas ,which tells us about bhraman. Who ever with devotion hear this ,gets freed from all the sins.
