Praise be to Allaah.
It is not permissible to bow when meeting someone, whether he is a scholar or anyone else.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
With regard to bowing when greeting someone, it is forbidden as is narrated in al-Tirmidhi from the Prophet (blessings and peace of Allah be upon him); they asked him about a man who meets his brother, can he bow to him? He said: No. And it is not permissible to bow or prostrate to anyone except Allah, may He be glorified and exalted, even though that may have been a form of greeting in other religions, as in the story of Yoosuf - â€¦and they fell down before him prostrate. And he said: O my father! This is the interpretation of my dream aforetime!' [Yoosuf 12:100]. But in our religion it is not acceptable to bow or prostrate to anyone except Allah; in fact it is also forbidden to stand as the non-Arabs stand before one another, so how about bowing and prostrating? Similarly, a partial bow is also included in this prohibition.
End quote from Majmoo al-Fataawa, 1/377
And he said:
With regard to lowering the head when meeting prominent figures such as shaykhs and so on, or kissing the ground and so on, these are things concerning which there is no difference of opinion among the imams that they are forbidden. In fact merely inclining the back to anyone other than Allah, may He be glorified and exalted, is forbidden. In al-Musnad and elsewhere it is narrated that when Muaadh ibn Jabal came back from Syria, he prostrated to the Prophet (blessings and peace of Allah be upon him), who said: What is this, O Muaadh? He said: O Messenger of Allah, I saw them in Syria prostrating to their bishops and patriarchs, and they narrated that from their Prophets. He said: They are lying, O Muaadh; if I were to instruct anyone to prostrate to anyone else, I would have instructed a woman to prostrate to her husband because of the greatness of his rights over her. O Muaadh, do you think that if you were to pass my grave you would prostrate? He said: No. He said: Do not do that, or words to that effect.
To sum up: standing, sitting, bowing and prostrating are due only to the only One Who is deserving of worship, the Creator of the heavens and the earth; with regard to that which is due only to Allah, no one should have any share in it; this also applies to swearing by anything other than Allah, may He be glorified and exalted.
End quote from Majmoo al-Fataawa, 27/92, 93
The scholars of the Standing Committee said:
It is not permissible to bow when greeting or to take off one's shoes for him.
And they said:
It is not permissible to bow when greeting a Muslim or a kaafir, whether with the upper part of the body or the head, because bowing is a form of worship, and worship can only be for Allah alone.
Shaykh Abd al-Azeez ibn Baaz, Shaykh Abd al-Razzaaq Afeefi, Shaykh Abd-Allah ibn Ghadyaan, Shaykh Abd-Allah ibn Qaood
Fataawa al-Lajnah al-Daa'imah, 1/233, 234
And Allah knows best.