In Turkish culture, one kisses the back of someone's hand to show respect. First he kisses the back of the person's hand, and then he he touches his forehead with it. Is this permissible? I read that it is permissible, but is this true? Should we warn the common people from taking advice from someone who says this?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

We have previously underlined that there is no harm in kissing the hand of some virtuous people who are worthy of respect. Please refer to fatwas 83692 and 86027. However, this should not turn into a habit, kissing everyone's hand. Fataawa An-Nawawi (book) reads, "It is recommended to kiss the hands of the pious and virtuous scholars, and it is disliked to kiss the hands of other than them."

As for placing the forehead on the person's hand, Shaykh ʻAbd Al-Muhsin Al-ʻAbbaad was asked about the custom practiced in some Islamic countries where the son kisses the hand of his father or mother and then puts it on his forehead. He replied, "We do not know of any basis for kissing the hand and placing it on the forehead, so it should not be done." Therefore, it should be avoided, especially given that it resembles prostration in a way.

We emphasize that the Muslims should adhere to the Sunnah when meeting others; which is shaking hands. Indeed, following the Sunnah yields great benefit. Abu Hurayrah reported that the Prophet, sallallaahu ‘alayhi wa sallam, said, "When the believer shakes his brother's hand, their sins fall the way the leaves of a tree fall." [Al-Bazzaar - Al-Albaani graded it saheeh (sound)]

Allah knows best.