Reference: al-Fataawa al-Muhimmah – Page 709
Question: Is it permissible for a woman to use her mouth in playing with her husband’s private part (oral sex) and likewise for the man [to use his mouth in playing with his wife’s private part]?
Response: I will respond to the likes of this question by saying:
This is from the actions of some of the animals, such as the dogs.
We have a general principle, and that is the Messenger (sal-Allaahu ‘alayhi wa sallam) forbade [us from] resembling the animals in other than what we are talking about (oral sex); Such as his forbidding the placing of the knees on the ground before the hands [when going into sujood] just as the camel does; And looking around [in the salaah] like a fox; And pecking [in the rukoo’ and the sujood] like a crow.
And since it is also known that the Prophet (sal-Allaahu ‘alayhi wa sallam) forbade [us from] resembling the disbelievers, then it is understood from this to be a prohibition; Also affirming the prohibition in what has preceded regarding the resembling of animals, especially since that which is known about them is their filthy nature; So, with regard to this action (oral sex), the Muslim must be far above and removed from resembling the animals.
 Shaykh al-Albaanee mentions in “Sifatus-Salaah” «When one of you performs sajdah, he should not kneel like a camel, but should place his hands before his knees.» Transmitted by Abu Daawood, Tammaam in al-Fawaa.id, and an-Nasaa.ee in Sunan as-Sughraa and Sunan al-Kubraa (47/1) with a saheeh isnaad.
It should be known that the way to differ from the camel is to place the hands before the knees, because the camel places its knees first; a camel’s “knees” are in its forelegs, as defined in Lisaan al-‘Arab and other books of the ‘Arabic language, and as mentioned by at-Tahaawee in Mushkil al-Aathaar and Sharh Ma`aani al-Aathaar. Also, Imaam Qaasim as-Saraqustee (rahima-hullaah) narrated in Ghareeb al-Hadeeth (2/70/1-2), with a saheeh isnaad, Abu Hurayrah’s statement, “No one should kneel the way a runaway camel does”, and then added, “This is in sajdah. He is saying that one should not throw oneself down, as a runaway [or untamed] camel does, hurriedly and without calmness, but he should go down calmly, placing his hands first, followed by his knees, and an explanatory marfoo` hadeeth has been narrated in this regard.” He then mentioned the hadeeth above. Shaykh al-Albaanee mentions in “Sifatus-Salaah”: Abu Hurayrah (radhi-yAllaahu ‘anhu) said: “My close friend (sal-Allaahu ‘alayhi wa sallam) forbade me from pecking in my prayer like a cockerel, from looking around like a fox, and from squatting like a monkey.” Transmitted by Tayaalisee, Ahmad and Ibn Abee Shaybah; it is a hasan hadeeth, as I have explained in my footnotes on al-Ahkaam (1348) by `Abdul Haqq Ishbeelee  Shaykh al-Albaanee mentions in “Sifatus-Salaah”: «Were this man to die in this state, he would die on a faith other than that of Muhammad, [pecking in his prayer as a crow pecks at blood]; he who does not make rukoo’ completely and pecks in his sujood is like the hungry person who eats one or two dates, which are of no use to him at all.» Transmitted by Abu Ya`laa in his Musnad (340/3491/1), Aajurree in al-Arba`een, al-Bayhaqee, at-Tabaraanee (1/192/1), Diyaa’ in al-Muntaqaa (276/1), Ibn `Asaakir (2/226/2, 414/1, 8/14/1, 76/2) with a hasan isnaad, and Ibn Khuzaymah declared it saheeh (1/82/1). Ibn Battah has a supporting mursal narration for the first part of the hadeeth, minus the addition, in al-Ibaanah (5/43/1).