Is it permissible for a married man to recite the marriage sermon (khutbat al-nikah) himself to secretly marry a divorced woman?

It is not permissible for a woman to marry herself off, nor for a man to marry her to himself, without the permission of her guardian (wali) and the presence of witnesses. This would not be a legitimate marriage. If the marriage takes place with the permission of the guardian and the presence of two witnesses, it is a valid marriage, even if it is not publicized, as publicizing it is merely recommended. When it comes to polygyny, justice among the wives is a prerequisite, and one should not embark upon it unless capable of fulfilling this condition.