Praise be to Allah the Lord of the Worlds.
It is permissible to kiss the hand of one`s parent in addition to that of scholars and righteous men. It was reported that Osamah Ibn Shoraik said {what means}: "We stood to the Prophet (PBUH) and kissed his hand." This was related by Abu Baker al-Moqrie` in the chapter {Kissing the hand, P.58}. Commenting on this narration, Ibn Hajar said, "It has a strong chain of narrators {Sanad}." Kindly check {Fateh al-Barie, Vol.11:P.57}.
Al-Baihaqhi narrated in al-Sunnan al-Kubra, Vol.7:P.101 from Tamim Ibn Salamah who said, "When Omar Bin al Khattaab came to Sham (Syria), Abu Obaidah Bin al-Jarrah received him and kissed his hand, then they started crying in private." Al-Baihaqie said, Tamim used to say, "Kissing the hand is an act of Sunnah."
However, it is disliked to kiss the hand of the people of consequence or money people. An-Nawawi says, "It is desirable to kiss the hand of the righteous, the ascetic, the scholar and other people of righteousness. On the other hand, it is highly undesirable to kiss someone`s hand because he is rich or he is a man of consequence. Al-Mutawali added that this is impermissible."{Al-Majmou`, Vol.4:P.636}.
Moreover, abu Baker al-Moqrie` has written a booklet on this subject while Ibn Hajar elaborated on it in his book {Fateh al-Barie, Vol.11:P.56-57} and mentioned many an evidence supporting it. For example, "Imam Malik disliked kissing the hand out of pride and glorification. However, he permitted kissing someone`s hand because he is religious, honorable or from the people of knowledge as means of drawing closer to Allah."
Accordingly, people of righteousness whose hands are being kissed should resist developing feelings of pride and glorification and start telling people to kiss their hands. He who likes to be seen by people as great is at loss in the sight of Allah while he who is modest Allah will elevate his status. However, we should kiss the hand of parents, scholars and the people of righteousness who are generous benefactors. And Allah the Almighty knows best