What is the maximum time period for a man to leave his wife separate without having sexual intercourse between them? (For instance, he went to a foreign country to earn a living.)
I heard that at the time of Umar(R.A), he made a fatwa of "four months period is the maximum time for a women to control herself from haraam without husband, so who even went for jihad should return after four months to fulfill his wife's Haq".
What is the fatwa of Shia and Sunni scholars about this?
There is no clear-cut answer to this issue. It is told that Omar Ibn ElKhattab asked his daughter (and possibly other women) on how long a woman can wait for her husband, and she answered "4-6 months", so he decided that soldiers should spend at most 6 months in duty.
However, this is not a final rule, and the ruling is subject to the wife's needs. Some women may be able to withstand loneliness for longer periods, while others may fall to temptations in shorter periods. Her security in the society also makes a difference.
For more detailed information, I'd like to refer you to a fatwa by Bin Baz.
In Shi3a ithna `Ashari fiqh, it's a unanimous ruling that unless some form of contract was entered into at the time of nikaH or the wife herself permits, a husband cannot refuse sexual intercourse with his wife beyond four months.
The following is by Sayyid al-Sistani:
2427 It is not permissible for the husband to abandon sexual intercourse with his youthful, permanent wife for more than 4 months, except when sexual intercourse is harmful to him, or involves unusually more effort, or when the wife herself agrees to avoid it, or if a prior stipulation to that effect was made at the time of Nikah by the husband. And in this rule, there is no difference between the situations when the husband is present, or on a journey, or whether she is a wife by permanent or temporary marriage. www.al-islam.org
This is by Sayyid al-Khoei (ar):
2427 It is not permissible for a man to abandon sexual intercourse with his young permanent wife for more than 4 months.
What is the maximum time a man can leave his wife alone? The husband can not avoid intimacy with his wife for more than four months without a legal excuse, unless his wife is satisfied. Of course, this is a special ruling if the husband or wife has no excuse, but if there is an excuse, it is absolutely permissible to leave it as long as the excuse remains.