Prashna-6-7-tān hovācaitāvadevā

Sri Shankara’s Commentary (Bhashya) translated by S. Sitarama Sastri
For this verse and the next verse.

Having thus instructed them, Pippalâda said to them: “Thus far, I know the supreme Brahman worthy to be known. There is nothing beyond this, more excellent or worthy to be known. This he said to remove any doubt in the minds of disciples, that there was yet something not known and to produce a belief in their minds that their object had been accomplished. Then, what did the disciples instructed by the preceptor, their purpose accomplished and finding no return for knowledge received, do for their preceptor is explained. They worshipped him by throwing handfuls of flowers at his feet and by prostrating before him. What they said is stated: ‘You are our father; because, you are the creator, by giving us knowledge of the Brahman—body, eternal, undecaying, deathless and fearless as it were—because you alone have helped us to cross by means of the boat of knowledge to the other shore (supreme emancipation characterised by the absence of return to samsâra) of the ocean of ignorance consisting in perverse knowledge and infested by such evils as birth, old age, death, sickness, misery, etc.; your being our father is more appropriate than others.’ Even that other father who creates the mere physical body is still to be worshipped most of all, in the world. What need be said of him who confers thorough immunity from fear?” This is the drift. Adoration to the great sages who transmitted the knowledge of Brahman. Adoration to the great sages. The repetition indicates regard.

Links
Various resources on the Prashnopanishad
Upanishad Series – Kena Upanishad Commentary by Swami Chinmayananda