it is common sense. the definition of ilaah - means free from imperfection.
do you worship a god that can be imperfect? and if that is the case, then the entire basis of belief in god is upended.
only a perfect God is not dependent, does not die, does not require food and drink, does not forget, does not lie, does not fear, does not have children. because all of these are imperfections and dependencies.
if god can be imperfect - al-iyadhu billah - then god could lie, could eat and drink, could run away from threats, could cower in fear, could have children. etc.
if you are a muslim - then ask yourself what is the difference between your faith and that of the greeks, romans, hindus and christians? zeus can have children - lusts after wives of other 'gods', poseidon can be imprisoned, shiva can flee from bhasmasura, and the son of god can be crucified on the cross. (na'udhu billah)
is this even a question, a muslim asks?
when alahazrat illustrated the implication of this belief of deobandis (because their top taghut ismayil paleed in his yakrozi said that his god should be capable of doing all things humans can do, else he would be deemed impotent)
given below is from yak-rozah of ismayil dihlawi, p.17. i also have an older version (see TKM appendices) but this is easier to read.
and his saying: "and it is [i.e. falsehood] impossible [muhal] because it is a flaw.; and a flaw for the Creator - exalted is He - impossible"
i [ismayil dihlawi] say: if muhal here means - intrinsically impossible [mumtaniy li dhatihi] such that it is not included in Divine Power - then we do not accept that the falsehood mentioned is impossible as written [in the statement above]. because to say that which is not consistent with what has occured [i.e. to lie]- and to tell the angels and prophets is not precluded from Divine Power, otherwise, it would imply [wa illa laazim aayad] that the power of humans would be greater than the Power of the Lord Almighty, because most humans have the power to tell [ilqaa] those they address [mukhatabin] things which are contrary to what has occurred [qaziyyah ghayr mutabiq li'l waqiy. in plain words: lies, falsehood].
yes, however, the mentioned falsehood [i.e. in the cited text, which says it is impossible] is contrary to Divine Wisdom, and therefore it is impossible due to extraneous reason [mumtaniy bi'l ghayr] and therefore, it is considered as perfection for the Truthful [Haqq], Glory to Him.
translating the mountain troll ismayil's blabbering above in the common tongue:
concerning the statement "falsehood is impossible because it is a flaw" said by scholars: if it means uttering falsehood per se - we do not accept that falsehood impossible for him intrinsically. because uttering falsehood is in the power of humans. and if god could not utter a lie,* it would mean that humans have more power than Him as they are able to lie. however, if you say it is impossible because it is contrary to Divine Wisdom, in that case, yet it is impossible but only due to an external condition [i.e. Divine Wisdom] and this is why it is deemed as perfection [i.e. not lying].
*i.e. say something not according to the actual occurrence] then this
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the deobandis are so heavily invested in the taqlid of their jahil imam - i.e. ismayil dihlawi the filthy heretic - that zameel devbandi believes that his god can have a defect. anyway, let them take this accursed belief in their graves and answer for it.
alHamdulillah, we muslims believe that our God Almighty is free from flaw; and NECESSARILY so, not because he 'chooses' to be free from flaw!
devbandis are exactly like the israelis - always playing victim even after committing the most heinous crimes. when alahazrat explained what the above implies in his sub'han al-subbuh, they keep howling like the accursed community they imitate - and cry wolf - saying alahazrat said heinous things about the Deity.
alahazrat was only showing the blasted nincompoops what their stupid belief entails: fatawa ridawiyyah, 15/370:
see the despicable pronouncement of the the ugly mulla (ismayil dihlawi) attempting to reject the statement of imams [of ahl al-sunnah] that: "falsehood is a flaw; and falsehood is muhal." the ugly mulla replies to this by saying: "we do not accept that it is intrinsically impossible. [muhal bi'z zaat] rather, by these evidences [that is his own concocted proofs fro his putrid belief mentioned in yak rozah] proves that it is possible [mumkin].
see how clearly and openly, in explicit words he admits that not only falsehood - but every kind of flaw and shortcoming is possible to be found in god.
bravo champion!
and in the blink of an eye* - he has hacked at the roots of transcendence [tanzih] and Glory [taqdis] of the Lord Almighty.
[his statement implies that god can be:] impotent, ignorant, stupid, lazy, blind, deaf, stuttering, dumb - all of these are possible according to his principle [because these are flaws and ismayil refuses to believe that it is NOT intrinsically impossible for god to have a flaw].
[furthermore] eating, drinking, defecating, urinating, falling sick, giving birth to a baby, drowsiness, sleeping - in fact dying - and resurrection, everything becomes possible [because all of these are flaws - and a god with the possibility of flaw can have all this].
in conclusion, thousands of fundamental beliefs of islam - and the only proof Muslims had in their hand for it - i.e., it is intrinsically impossible [muhal bi'z zaat] for the Lord-Almighty to have a flaw - was rendered invalid by [this fool] and thus, we will have no proof [if we are asked, why can't god do all this.]
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*literally: in half the time of an eye can move
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if you are a muslim, you ask this question yourself.
do we also have rational evidence for Allah being pure from all imperfections or atleast impossibility of lie in divine speech.
that is the basis of many beliefs and in fact one of the key principles for belief in God.
Allah ta'ala knows best.