Permissibility of Ambiguity and Definition of Necessity
Question

                When is deliberate ambiguity valid? If that is in cases of necessity only, then what is the definition of necessity in this case?
Praise be to Allah.
    The Arabic word tawriyah [translated here 
    as deliberate ambiguity] means to conceal something.

    Allah says (interpretation of the 
    meaning): 

    “Then Allah sent a crow who scratched the 
    ground to show him how to hide [yuwaari] the dead body of his brother. He 
    (the murderer) said: “Woe to me! Am I not even able to be as this crow and 
    to hide the dead body of my brother?” Then he became one of those who 
    regretted” [5:31] 

    “O Children of Adam! We have bestowed 
    raiment upon you to cover yourselves (screen your private parts – yuwaari 
    saw’aatikum) and as an adornment; and the raiment of righteousness, that is 
    better. Such are among the Ayaat (proofs, evidences, verses, lessons, signs, 
    revelations, etc.) of Allaah, that they may remember (i.e. leave falsehood 
    and follow truth)”

    [al-A’raaf 7:26] 
With 
    regard to the meaning in sharee’ah (religious) terminology, it refers to 
    someone who says something that may appear to have one meaning to the 
    listener but the speaker intends something different that may be understood 
    from these words. For example, he says, “I do not have a dirham in my 
    pocket,” and that is understood to mean that he does not have any money at 
    all, when what he means is that he does not have a dirham but he may have a 
    dinar, for example. This is called ambiguity or dissembling. 

    Deliberate ambiguity is regarded as a 
    legitimate solution for avoiding difficult situations that a person may find 
    himself in when someone asks him about something, and he does not want to 
    tell the truth on the one hand, and does not want to lie, on the other. 

    Deliberate ambiguity is permissible if it 
    is necessary or if it serves a shar’i (religious) interest, but it is not 
    appropriate to do it a great deal so that it becomes a habit, or to use it 
    to gain something wrongfully or to deprive someone of his rights.  

    Al-Nawawi said: 
The 
    scholars said: If that is needed to serve some legitimate shar’i interest 
    that outweighs the concern about misleading the person to whom you are 
    speaking, or it is needed for a reason that cannot be achieved without 
    lying, then there is nothing wrong with using deliberate ambiguity as an 
    acceptable alternative. But if there is no interest to be served and no 
    pressing need, then it is makrooh (disliked), but is not haram 
    (impermissible). If it is a means of taking something wrongfully or 
    depriving someone of their rights, then it is haram in that case. This is 
    the guideline in this matter. Al-Adhkaar. 

    Some scholars were of the view that it is 
    haram to resort to deliberate ambiguity if there is no reason or need to do 
    so. This was the view favoured by Shaykh al-Islam Ibn Taymiyah (may Allah 
    have mercy on him). See al-Ikhtiyaaraat. 

    There are situations in which the Prophet 
    (peace and blessings of Allah be upon him) taught that we may use deliberate 
    ambiguity, for example: 

    If a man loses his wudoo (ablution) whilst 
    praying in congregation, what should he do in this embarrassing situation? 

    The answer is that he should place his 
    hand over his nose and leave. 

    The evidence for that is the report 
    narrated from ‘Aishah (may Allah be pleased with her) who said: The 
    Messenger of Allah (peace and blessings of Allah be upon him) said: “If 
    anyone of you breaks his wudoo whilst praying, let him hold his nose and 
    leave.” Sunan Abi Dawood. 
Al-Teebi 
    said: The command to hold his nose is so that it will look as if he has a 
    nosebleed. This is not a lie, rather it is a kind of ambiguity. This 
    concession is granted so that the Shaytan will not trick him into staying 
    put because of feeling embarrassed in front of people. 
Mirqaah 
    al-Mafaateeh Sharh Mishkaat al-Masaabeeh.  

    This is a kind of ambiguity that is 
    permitted, so as to avoid any embarrassment and so that whoever sees him 
    leaving will think that he has a nosebleed.

    Similarly If a Muslim faces a difficult 
    situation where he needs to say what is against the truth in order to 
    protect himself or someone who is innocent, or to save himself from serious 
    trouble, is there a way for him to escape the situation without lying or 
    falling into sin?

    Yes, there is a legal way and a 
    permissible escape that one can make use of if necessary. It is equivocation 
    or indirectness in speech. Imam al-Bukhaari (may Allah have mercy on him) 
    entitled a chapter of his Saheeh: “Indirect speech is a safe way to avoid a 
    lie”. (Saheeh al-Bukhari, Kitaab al-Adab (Book of Manners)).

    Equivocation means saying something which 
    has a closer meaning that the hearer will understand, but it also has a 
    remote meaning which what is actually meant and is linguistically correct. 
    The condition for this is that whatever is said should not present a truth 
    as falsity and vice versa. The following are examples of such statements 
    used by the salaf (pious predecessors) and early imams (religious leaders), 
    and collected by Imam Ibn al-Qayyim in his book Ighaathat al-Lahfaan:

    It was reported about Hammad (may Allah 
    have mercy on him), if someone came that he did not want to sit with, he 
    would say as if in pain: “My tooth, my tooth!” Then the boring person whom 
    he did not like would leave him alone.

    Imam Sufyan Al-Thawri was brought to the 
    khaleefah al-Mahdi, who liked him, but when he wanted to leave, the 
    khaleefah told him he had to stay. Al-Thawri swore that he would come back. 
    He then went out, leaving his shoes at the door. After some time he came 
    back, took his shoes and went away. The khaleefah asked about him, and was 
    told that he had sworn to come back, so he had come back and taken his 
    shoes.

    Imam Ahmad was in his house, and some of 
    his students, including al-Mirwadhi, were with him. Someone came along, 
    asking for al-Mirwadhi from outside the house, but Imam Ahmad did not want 
    him to go out, so he said: “Al-Mirwadhi is not here, what would he be doing 
    here?” whilst putting his finger in the palm of his other hand, and the 
    person outside could not see what he was doing.

    Other examples of equivocation or 
    indirectness in speech include the following:

    If someone asks you whether you have seen 
    so-and-so, and you are afraid that if you tell the questioner about him this 
    would lead to harm, you can say “ma ra aytuhu”, meaning that you have not 
    cut his lung, because this is a correct meaning in Arabic [“ma ra aytuhu” 
    usually means “I have not seen him,” but can also mean “I have not cut his 
    lung”]; or you could deny having seen him, referring in your heart to a 
    specific time and place where you have not seen him. If someone asks you to 
    swear an oath that you will never speak to so-and-so, you could say, 
    “Wallaahi lan ukallumahu”, meaning that you will not wound him, because 
    “kalam” can also mean “wound” in Arabic [as well as “speech”]. Similarly, if 
    a person is forced to utter words of kufr (disbelief) and is told to deny 
    Allah, it is permissible for him to say “Kafartu bi’l-laahi”, meaning “I 
    denounce the playboy” [which sounds the same as the phrase meaning “I deny 
    Allah.”]

    (Ighaathat al-Lahfaan by Ibn al-Qayyim. 
    See also the section on equivocation (ma’aareed) in Al-Adaab al-Shar’iyyah 
    by Ibn Muflih).

    However, one should be cautious that the 
    use of such statements is restricted only to situations of great difficulty, 
    otherwise:

    Excessive use of it may lead to lying.

    One may lose good friends, because they 
    would always be in doubt as to what is meant.

    If the person to whom such a statement is 
    given comes to know that the reality was different from what he was told, 
    and he was not aware that the person was engaging in deliberate ambiguity or 
    equivocation, he would consider that person to be a liar. This goes against 
    the principle of protecting one’s honour by not giving people cause to doubt 
    one’s integrity.

    The person who uses such a technique 
    frequently may become proud of his ability to take advantage of people.  

    End quote. From Madha taf’al fi’l-haalaat 
    al-aatiyah (What to do in the following situations)? 

    And Allah knows best.