Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- The way this hadith describes the rights of the husband over his wife in such repulsive language is alien and odd compared to the commonly used language in the Sunnah of the Prophet (peace be upon him).
2- Even if we assume that the hadith in reference is authentic, its sole intention is to express the greatness of the rights of the husband over his wife.
Elaborating more on this hadith, the Fatwa Center at Islamweb.net, states the following:
The hadith in reference is cited in Al-Musnad and in other Hadith collections. The most likely correct view is that it is weak and cannot be attributed to the Prophet (peace be upon him) due to the weakness of its chain of narration and the strange, rejected language of its text, despite the fact that some Hadith scholars reinforced it as a result of Ijtihad (independent reasoning).
Shaykh ‘Abdullaah Al-Juday’ wrote about the signs of the hidden defects of hadiths according to the early Hadith scholars:
“A hadith is declared Munkar (rejected) when the Hadith critic detects signs of weakness and hidden defects that are unbecoming of divine revelation and the language of the Prophet (peace be upon him). A good example on the signs of weakness is the hadith narrated on the authority of Abu Sa‘eed Al-Khudri, ‘Even if a woman licks the puss of her husband flowing from head to toe…’
For long, I had a strong feeling regarding the weakness of this hadith, until I became convinced of its weakness. The way this hadith describes the rights of the husband over his wife in such repulsive language is alien and odd compared to the commonly used language in the Sunnah of the Prophet (peace be upon him), who used to keenly choose the most thoughtful and gentle words and who was granted wisdom, eloquence, and the ability to produce words that are concise but comprehensive in meaning.
Allah, The Exalted, has underlined the rights of the husband over his wife in the Quran and the Sunnah of His Messenger (peace be upon him), who was endowed with the refined and noble character, in the most refined and comprehensive statements. For instance, Allah, The Exalted, says (what means): {And due to the wives is similar to what is expected of them, according to what is reasonable.} [Al-Baqarah 2:228].” [Tahreer ‘Uloom Al-Hadith, 2/757]
Even if we assume that the hadith in reference is authentic, its sole intention is to express the greatness of the rights of the husband over his wife. This meaning is established by many other authentic and collectively contiguous religious texts. It does not mean that the wife is enjoined to actually lick puss flowing from her husband, because it is impure and filthy. Rather, it is meant as an exaggeration to emphasize the great rights of the husband over his wife.
As-San‘aani wrote, “Clearly, the simile in this hadith is meant to stress the right of the husband.” [At-Tanweer Sharh Al-Jaami‘ As-Sagheer]
As for your question, “Why does Islam state that a husband has a greater right than the wife? Is that not unfair?,” you should know that this is an inappropriate question because it implies objection to the words of Allah and His decree.
Allah, The Exalted, says (what means): {But the men have a degree over them (in responsibility and authority).} [Al-Baqarah 2:228]
Ibn Katheer wrote:
“This verse indicates that men are in a more advantageous position than women physically as well as in their status, the enjoined obedience (of women to them), spending, the duty of being in charge and taking care of affairs, and their favor in this life and in the Hereafter. Allah, The Exalted, says (what means): {Men are in charge of women by (right of) what Allah has given one over the other and what they spend (for maintenance) from their wealth.} [An-Nisaa 4:34]”
As for your remark that since Islam teaches that the husband has greater rights over his wife, this implies injustice, you should know that it does not constitute injustice towards the woman in the slightest. Emphasizing the greater rights of someone over another does not imply wronging the other. For example, when we say that parents have greater rights over their children, does this imply wronging the children?
It is known to wise people that the rights granted to the person correspond with the responsibilities assigned to him or her; with privilege comes responsibility.
This does not imply injustice towards the others to whom less responsibilities and duties are assigned. The problematic aspect of the issue of the rights of the husband over his wife is due to the Western feminist calls that clash with the Shari`ah and sound human nature and promote the illusionary equality between men and women in all aspects.
For more, see these fatwa:
Is Gender a Factor in Reward and Punishment?
Scope of Men’s Guardianship over Women
Almighty Allah knows best.