WHO IS CONSIDERED TO BE MAHRAM FOR MUSLIM MEN:

Any woman, with whom a man has a relationship (of blood or foster) that precludes marriage, is considered a mahram to him. Mahram women include his mother, grandmother, daughter, granddaughter, sister, aunt, grandaunt, niece, grandniece, his father's wife, his wife's daughter, his mother-in-law, his foster mother , foster sisters, and any foster relatives that are similar to the above mentioned blood relatives.

IN SURAH NOOR , ALLAH RABB UL IZAT ORDERS MUSLIM MEN:

"And marry not women whom your fathers married, except what has already passed; indeed it was shameful and most hateful, and an evil way. Forbidden to you (for marriage) are: your mothers, your daughters, your sisters, your brother's daughters, your sister's daughters, your foster mother who breastfed you, your foster sisters, your wives' mothers, your stepdaughters under your guardianship, born of your wives to whom you have gone in -but there is no sin on you if you have not done so (to marry their daughters), the wives of your sons who spring from your loins, and two sisters in wedlock at the same time, except for what has already passed; verily Allah is Oft-Forgiving, Most Merciful. " [4:22-23]

All the man's female relatives mentioned in these verses are considered his mahrams, because it is unlawful (haram) for him to marry them, except the wife's sister mentioned last, who is not a mahram because he can marry her if he divorces his wife, or if she dies.
WHO IS CONSIDERED TO BE A MAHRAM FOR MUSLIM WOMEN:


24:31] "And say to the believing women that they should lower their gaze and guard their modesty; that they should not display their beauty and ornaments except what (must ordinarily) appear thereof; that they should draw their veils over their bosoms and not display their beauty except to their husbands, their fathers, their husband's fathers, their sons, their husbands' sons, their brothers or their brothers' sons, or their sisters' sons, or their women, or the slaves whom their right hands possess, or male servants free of physical needs, or small children who have no sense of the shame of sex; and that they should not strike their feet in order to draw attention to their hidden ornaments. And O ye Believers! turn ye all together towards Allah, that ye may attain Bliss".

In this verse not only those who are MAHRAM for a Muslim women are mentioned but also ALLAH ALMIGHTY'S CLEARCUT ORDERS about lowering their gaze is given.
SHAKING HANDS WITH NA-MEHRAM

The traditions of certain societies have prevailed over Allah's Shari'ah concerning this matter. Their wrong habits have overcome the rule of religion so much so that when one presents the rule of the Shari'ah to them, he is accused of being backward.

Shaking the hand of one's female cousins, or one's uncles' wives has become as easy as falling off a log in our societies, but if people considered seriously the dangers of this matter in the Shari'ah, they would not do it. The Prophet, sallallahu alayhe wa sallam, said,
It is better for one of you to be pierced by an iron needle in the head than to touch the hand of a woman that is not allowed to him." (Tabarani)

This sin is considered a fornication of the hand, as the Prophet, sallallahu alayhe wa sallam, said, "The eyes fornicate, and the hands fornicate, and the feet fornicate, and the intimate parts fornicate." (Ahmad)

Is there a person purer than Muhammad, sallallahu alayhe wa sallam? And in spite of that he said, "I do not shake women's hands." (Ahmad) He also said, "I do not touch women's hands." (Tabarani)

Aisha, radhiallahu anha, said, "No by Allah, the Prophet's hand never touched a woman's hand, he used to accept their pledge of allegiance by [hearing their] words only." (Muslim)

Men who threaten to divorce their pious wives if they refuse to shake their brothers' hands should fear Allah. It should also be known that wearing a glove or wrapping the hand with a cloth while shaking hands is not allowed either.
MAY ALLAH ALMIGHTY HELP ALL MUSLIM UMMAH TO FOLLOW HIS COMMANDS COMPLETELY ANDMAY WE ALL MUSLIMS GET COMPLETE UNDERSTANDING OF THESE WARNING WORDS OF ALLAH ALMIGHTY,SO THAT WE MAY BE SAVED FROM ALLAH ALMIGHTY'S ANGER AND RASOOL ALLAH (SAW)' S ANNOYANCE IN BOTH THE WORLDS .AMEEN.

33:36]"It is not fitting for a Believer, man or woman, when a matter has been decided by ALLAH and His Messenger to have any option about their decision: if any one disobeys ALLAH and His Messenger, he is indeed on a clearly wrong Path".

JAZAK ALLAH KHAIR