In Sanathan dharma, there are four varnas: Brahmin, Kshetriya, Vaishya, and Shudra. It is well known that, in general, Kshatriyas and other orders pay respect, and give honor to Brahmins due to their lifestyle and several other aspects.
One such expression of honor can be seen in the Mahabharatha where Krishna washes the feet of Brahmins during Yudhishthira's Rajasuya
The eldest of the sons of Pandu, who had been installed at the sacrifice, having said this unto all, appointed every one of them to suitable offices. He appointed Dussasana to superintend the department of food and other enjoyable articles. Aswatthama was asked to attend on the Brahmanas. ....Duryyodhana became the receiver of the tributes that were brought by the kings. Krishna who was himself the center of all worlds and round who moved every creature, desirous of acquiring excellent fruits, was engaged at his own will in washing the feet of the Brahmanas.
[Section 34, Rajasuyika Parva, Sabha Parva, The Mahabharata]
While mentioning this incident, Babasaheb Dr. B.R. Ambedkar expressed his opinion, as follows, in his writing THE RIDDLE OF RAMA AND KRISHNA
In due course the Rajasuya came off. Of the various functions and duties connected with the ceremony, Krishna is said to have taken charge of washing the feet of the Brahmans. This is a sure indication of the comparative modernness of the Mahabharata, at any rate, of this story. For in ancient times, even when the supremacy of the Brahmans had been established, the Kshatriyas never paid them any servile honor.
He is claiming that Kshatriyas never paid any servile honor to Brahmins in ancient times.
In this context, I want to know the incidents similar to the one in the first quote, ancient in nature, where Kshatriyas pay servile honor to Brahmins. What are those incidents?