What is the meaning of the phrase: "And by analogy: whatever is permissible to be replaced or compensated for, it is permissible to be given as a gift," which appears in "Al-Tamheed" in the context of the discussion about the woman who offered herself to the Messenger of Allah, peace and blessings be upon him?

A condition for a gift (hiba) is that the gifted item must have financial value, such that it can be exchanged for money. It is not permissible to gift something that is not property or that has no value, like carrion or wine. Although a woman has financial value in marriage (the dower/mahr), Islamic law has prohibited her from gifting herself. The marriage of gifting (nikah al-hiba) was reserved exclusively for the Messenger of Allah, peace be upon him. The dower (mahr) is a condition for marriage by consensus, and it is not permissible to agree to waive it. However, it is permissible for the wife to gift the dower to her husband after she takes possession of it, as stated in the Almighty's saying: "And give the women [in marriage] their dowries as a free gift; but if they should be kind enough to give back to you a part of it, consume it with good cheer and ease." (An-Nisa/4).