Is the marriage of a sheikh to a fifth wife, when he already has four, after her brother offered her to him as a gift, valid, and would this cause the emergence of innovations (bid’ah) and distort the image of the religion?

It is impermissible for a Muslim to combine more than four wives, by consensus, due to the Almighty's saying: (Marry such women as seem good to you, two, three, or four) [An-Nisa: 3]. And due to the Prophet's (peace and blessings be upon him) command to Ghaylan ibn Salamah to keep four and separate from the rest when he embraced Islam, as he had ten wives.

Marriage to a fifth wife is invalid. If the husband is aware of its prohibition, he is considered an adulterer, and his children from this woman are not attributed to him. However, if he is ignorant of the legal ruling, the marriage is invalid, but the children are attributed to him by agreement, because the establishment of lineage does not depend on the validity of the marriage as long as the husband believes it to be a permissible marriage.

As for a woman offering herself to a man, it is invalid. Even if it were considered a valid marriage, it is a prerogative of the Prophet (peace and blessings be upon him). And if he considers her his slave, that is even more corrupt, as a free person cannot offer themselves as a slave.

The man must repent to Allah from this serious sin, especially if he is an example to others.