In the name of Allah, the Beneficent, the Merciful,

All praise is due to Allah and may peace and blessing be upon the Messenger of Allah, his family, companions and true followers.

To proceed: The basic principle is that it is prohibited to shake hands with a "foreign" (non-mahram) woman due to the unequivocal, authentic evidence related on the issue. Among that we mention: the hadith of Ma`qal ibn Yasar, who said, "The Messenger of Allah (may Allah bless him and grant him peace) said, 'That one of you should be pierced in the head with an iron needle would be better for him than that he touch a woman who is not permissible for him." [Related by Al-Tabarani in his book, Al-Kabir (486); Al-Albani also said in his book, Sahih al-Jaami`a (5045): authentic] There is also the hadith related by Imam Muslim on the authority of `Urwah that Aishah told him about the women's pledge of allegiance. She said, "Allah's Messenger (may Allah bless him and grant him peace) never touched a woman with his hand, ever; rather he would take it [the pledge] from her [verbally]. So, when he had taken it and she gave it to him, he would say, 'Go, for I have accepted your allegiance.'"

Waliy-ud-deen al-Iraqi said in his book, Tarh al-Tathrib:

And in it [this hadith is the point]: that the hand of Allah's Messenger (saws) never touched the hand of a woman, ever, except for his wives or [the captives and slaves] that his right hand possessed, not in a pledge of allegiance nor anything else, and if he did not do that despite the fact that he was protected from sin and that there was absolutely nothing suspicious about [his intentions], then others are even more in need of this [not touching women].

The discussions of the leading scholars of fiqh are plentiful in that. As such, it is necessary for the Muslim to take precautions in this issue as much as possible. It should be known about him that he abstains from this for religious reasons out of respect for women and to protect them, not out of condescension or disdain for them. Then, if he is overcome in a certain situation, he should ask Allah for forgiveness afterwards.

{And whosoever does evil or wrongs himself, but afterwards seeks Allah's Forgiveness, he will find Allah Oft-Forgiving, Most Merciful.}

[Al-Nisaa 4: 110]

We ask Allah to grant us and him repentance and forgiveness.