Definition of divorce:
Divorce in language is lifiting restriction. (1)
According to jurists, it is a legal ruling to lift the restriction of marriage with certain wordings. (2)
The wisdom behind the permissibility of divorce:
Indeed, Allah (may He be Exalted) legislated marriage for the interest of people as it regulates the worldly and religious affairs of people. Then Allah legislated divorce to complete the best interest because marriage may not be suitable for some people, so divorce comes to enable him to break the marriage. There is a deferred wisdom which is a person will try himself in separation as he had tried it in marriage. Then Allah prohibited the wife for her husband after the end of the three times of divorce and she has to marry another person in order to discipline a husband by seeing the second husband marrying his ex-wife. At that moment, the continuation of marriage will be a corruption and harm by forcing a husband to spend on his wife and live with her despite his bad treatment to her and permanent rivalry without any use, so divorce is inventible to remove the corruption and harm. (3)
The wisdom behind divorce in the hand of men without women:
Ibn Al Qayyim (may Allah bestow mercy on his soul) said: Allah (Glory be to Him) made divorce in the hand of men instead of women out of His Mercy and Benevolence and for maintaining the interests of both spouses. Yes, a husband may give his wife the choice in staying with him or preferring separation and divorce. However, it is not permissible that a husband will not have an upper hand over his wife. Moreover, he has no right to forsake his right of having his wife back in marriage because the Lawgiver grants a person the rights which are useful for him and do not cause any harm to him, therefore, it did not give the husband more than three times divorce and a husband does not have the right to combine the three divorces in one, and did not give him the right of divorce in menstrual period nor in non-menstrual period where sexual intercourse took place, did not permit him to marry more than four wives and did not grant the wife the right of divorce. Allah (Glory be to Him) prohibited men to give the foolish their property which Allâh has made a means of support for you, so how could husbands give their wives the matter of divorce and coming back in marriage! As long as divorce is not in her hand, going back in marriage should not be left to her. (4)
(1) See As-Sihah Fi Al Lughah 1/428 and Lisan Al `Arab 10/225.
(2) See: Al `Inayah 5/160, Tabiin Al Haqa'iq 2/188, Al Bahr Ar-Ra'iq 3/253, Mughny Al Muhtaj 3/279, Al Mughny 8/234, and Al Mubdi` 7/230 but they did not say with certain wordings.
(3) See: Al `Inayah 5/160, and Al Mughny 8/235.
(4) Zad Al Ma`ad 5/676.