We find the following three verses at the beginning of the Taittiriya Bhashyam:
यस्माज्जातं जगत्सर्वं यस्मिन्नेव प्रलीयते ।
येनेदं धार्यते चैव तस्मै ज्ञानात्मने नमः ॥ १ ॥
यैरिमे गुरुभिः पूर्वं पदवाक्यप्रमाणतः ।
व्याख्याताः सर्ववेदान्तास्तान्नित्यं प्रणतोऽस्म्यहम् ॥ २ ॥
तैत्तिरीयकसारस्य मयाचार्यप्रसादतः ।
विस्पष्टार्थरुचीनां हि व्याख्येयं सम्प्रणीयते ॥ ३ ॥
While the first verse is an obeisance to Brahman, both Saguna and Nirguna, the second one is to his purva Acharyas who have commented/elucidated upon the Vedantas based on the aids such as vyakarana, mimamsa and nyaya. The third verse is acknowledging the grace of his Acharya/s, blessed with which he commences the elucidation of the Taittiriya Upanishad.
Interestingly we find similar, almost same, wordings in Shankara's opening and closing verses for the 17th chapter of the Upadeshasahasri:
Here the idea of nirguna and saguna Brahman is brought out for obeisance.
Almost the same as the 2nd verse in the Tai.Up.bhashya above.
Here Shankara says he has acquired the knowledge, realization, by the words of his Acharyas. Having bowed to them, he started his exposition of the purport of the Vedanta, Brahmavidya.
At the end of this chapter, Shankara once again revers Brahman and the Acharya:
Here the obeisance is to Brahman, in its nirguna mode and also saguna mode (second line first two epithets).
Shankara acknowledges the teaching of the Acharyas which resulted in his liberation that is crossing over the ignorance-filled ocean of bondage.
Shankara has made similar benedictory verses at the beginning and the end of the Mandukya (and Karika) bhashya.
Sureshwaracharya, in his Naishkarmya siddhi, has cited verses from the Upadesha sahasri (and the Mandukya Karika) and acknowledged them as that of the Acharya. (He refers to Gaudapada as Gauda and Shankaa as Dravida with respect)
Om Tat Sat
subbu