[Ruling on Marriage to a Flagranly Sinful Person, a Hypocrite, or Someone of a Different Madhhab]

Answer—with Allah’s help:
 It is not permissible for the guardian (walī) of a believing woman to marry her to a flagrantly sinful man, a hypocrite, or someone opposed to her in madhhab. He may only marry her to someone aligned with her madhhab.
 If he marries her to a man of outwardly upright conduct who is aligned in madhhab, and later the man’s madhhab changes to one that opposes hers, or his hypocrisy becomes manifest, etc., then what is obligatory upon the wife is to safeguard her religion and creed. There is no sin upon her in remaining with her husband, nor is any blame attached to her, and the marriage is not dissolved except by a judge’s ruling.
The proof for this is the agreed principle that a guardian must consider the best interests of the one under his guardianship in all his dispositions, indeed the most beneficial when interests conflict. Hence the ḥadīth: “Each of you is a shepherd, and each of you will be questioned about his flock.”
 Allah only legislated public and private forms of guardianship to preserve the interests of those under guardianship and ward off harms to their religion and worldly life. He said: “They ask you about the orphans. Say, ‘Improvement for them is best; and if you mix with them, they are your brothers. Allah knows the corrupter from the reformer …’ ” [al-Baqara: 220].
 Thus, if a guardian marries a believing woman to a fāsiq, a hypocrite, or someone of an opposing madhhab, he has been negligent in his guardianship, betrayed the trust, and failed what Allah entrusted to him—disobeying Allah Most High. However, the marriage is valid, because the only condition for the validity of marriage is the outward profession of Islam.
 As for a believing man, there is no harm in his marrying a woman who opposes him in madhhab, or a hypocrite, etc., provided she is chaste—though marrying a believing woman is better and purer.
We said this in contrast to the reverse case, because the common pattern is that a wife follows her husband’s religion without strain, and marriage to such a woman may become a cause for her rectification. In the ḥadīth: “O ʿAlī, that Allah guides a single person by your hand is better for you than whatever the sun rises upon.”
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.1